1.
Passivity (engineering)
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Passivity is a property of engineering systems, used in a variety of engineering disciplines, but most commonly found in analog electronics and control systems. A passive component, depending on field, may be either a component that consumes energy, a component that is not passive is called an active component. An electronic circuit consisting entirely of passive components is called a passive circuit, used out-of-context and without a qualifier, the term passive is ambiguous. Typically, analog designers use this term to refer to incrementally passive components and systems, systems for which the small signal model is not passive are sometimes called locally active. Systems that can power about a time-variant unperturbed state are often called parametrically active. In control systems and circuit theory, a passive component or circuit is one that consumes energy. Circuit designers will sometimes refer to this class of components as dissipative, while many books give definitions for passivity, many of these contain subtle errors in how initial conditions are treated. Below is a correct, formal definition, taken from Wyatt et al, a system is considered passive if EA is finite for all initial states x. Otherwise, the system is considered active, roughly speaking, the inner product ⟨ v, i ⟩ is the instantaneous power, and EA is the upper bound on the integral of the instantaneous power. This upper bound is the energy in the system for the particular initial condition x. If, for all initial states of the system, the energy available is finite. In circuit design, informally, passive components refer to ones that are not capable of power gain, under this definition, passive components include capacitors, inductors, resistors, diodes, transformers, voltage sources, and current sources. They exclude devices like transistors, vacuum tubes, relays, tunnel diodes, formally, for a memoryless two-terminal element, this means that the current–voltage characteristic is monotonically increasing. For this reason, control systems and circuit network theorists refer to these devices as locally passive, incrementally passive, increasing, monotone increasing, or monotonic. This term is used colloquially in a number of contexts, A passive USB to PS/2 adapter consists of wires. An active USB to PS/2 adapter consists of logic to translate signals A passive mixer consists of just resistors, in audio work one can also find both passive and active converters between balanced and unbalanced lines. In some very informal settings, passivity may refer to the simplicity of the device, here, devices like diodes would be considered active, and only very simple devices like capacitors, inductors, and resistors are considered passive. In some cases, the linear element may be a more appropriate term than passive device
2.
Anode
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An anode is an electrode through which conventional current flows into a polarized electrical device. A common mnemonic is ACID for anode current into device, the direction of electric current is opposite to the direction of electron flow, electrons flow out the anode to the outside circuit. The terms anode and cathode do not relate to the polarity of those electrodes but the direction of the current. Conventional current quantifies the flow of positive charge, in most cases, positive charge leaves the device via the cathode, and positive charge flows into the device via the anode. Conventional current depends not only on the direction the charge carriers move, the currents outside the device are usually carried by electrons in a metal conductor. The flow of electrons is opposite to conventional current because electrons have a negative charge, consequently, electrons leave the device via the anode, and electrons enter the device through the cathode. The anode and cathode have slightly different definitions for electrical devices such as diodes and vacuum tubes where the naming is fixed. These devices usually allow substantial current flow in one direction but negligible current in the other direction, consequently, the electrode names use the terms that have substantial ordinary currents. An ideal diode allows current in one direction but not in the other, for the ideal diode, it makes sense to always call that terminal the anode. For non-ideal diodes, the electrodes are also given fixed names even though such a diode under reverse bias would have a positive charge out of the anode. For some operating conditions and devices, such as diode breakdown, Zener diodes, or photodiodes, the polarity of voltage on an anode with respect to an associated cathode varies depending on the device type and on its operating mode. This inward current is carried externally by electrons moving outwards, negative charge flowing in one direction being electrically equivalent to positive charge flowing in the opposite direction. In a recharging battery, or a cell, the anode is the positive terminal. In a diode, the anode is the terminal at the tail of the arrow symbol. Note electrode naming for diodes is always based on the direction of the forward current, in a cathode ray tube, the anode is the positive terminal where electrons flow out of the device, i. e. where positive electric current flows in. The use of East to mean the in direction may appear contrived, previously, as related in the first reference cited above, Faraday had used the more straightforward term eisode. The reference he used to effect was the Earths magnetic field direction. In electrochemistry, the anode is where oxidation occurs and is the positive polarity contact in an electrolytic cell, at the anode, anions are forced by the electrical potential to react chemically and give off electrons which then flow up and into the driving circuit
3.
Cathode
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A cathode is the electrode from which a conventional current leaves a polarized electrical device. A conventional current describes the direction in which positive electronic charges move, Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic cathode current departs also means that flow into the devices cathode. Cathode polarity with respect to the anode can be positive or negative and this outward current is carried internally by positive ions moving from the electrolyte to the positive cathode. It is continued externally by electrons moving inwards, this negative charge moving inwards constituting positive current flowing outwards, for example, the Daniell galvanic cells copper electrode is the positive terminal and the cathode. In a recharging battery, or an electrolytic cell performing electrolysis, for example, reversing the current direction in a Daniell galvanic cell would produce an electrolytic cell, where the copper electrode is the positive terminal and the anode. In a diode, the cathode is the terminal at the pointed end of the arrow symbol. Note, electrode naming for diodes is always based on the direction of the forward current, an electrode through which current flows the other way is termed an anode. The use of West to mean the out direction may appear unnecessarily contrived, previously, as related in the first reference cited above, Faraday had used the more straightforward term exode. The reference he used to effect was the Earths magnetic field direction. The flow of electrons is almost always from anode to cathode outside of the cell or device, regardless of the cell or device type, an exception is when a diode reverse-conducts, either by accident or by design. In chemistry, a cathode is the electrode of a cell at which reduction occurs. Another mnemonic is to note the cathode has a c, as does reduction, perhaps most useful would be to remember cathode corresponds to cation and anode corresponds to anion. The cathode can be negative like when the cell is electrolytic, the cathode supplies electrons to the positively charged cations which flow to it from the electrolyte. The cathodic current, in electrochemistry, is the flow of electrons from the interface to a species in solution. The anodic current is the flow of electrons into the anode from a species in solution, in an electrolytic cell, the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or pure metal from metal ions, when discussing the relative reducing power of two redox agents, the couple for generating the more reducing species is said to be more cathodic with respect to the more easily reduced reagent. When metal ions are reduced from ionic solution, they form a metal surface on the cathode
4.
Electronic symbol
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An electronic symbol is a pictogram used to represent various electrical and electronic devices in a schematic diagram of an electrical or electronic circuit. These symbols can vary from country to country, but are today to a large extent internationally standardized, some symbols represent components which ceased to be used routinely as newer technologies were introduced. There are several national and international standards for graphical symbols in circuit diagrams, in particular, IEEE Std 91/91a, graphic symbols for logic functions. It is referenced in ANSI Y32. 2/IEEE Std 315, different symbols may be used depending on the discipline using the drawing. For example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics, national and local variations to international standards also exist. Symbols shown are typical examples, not a complete list
5.
Electronics
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Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements, the science of electronics is also considered to be a branch of physics and electrical engineering. The ability of electronic devices to act as switches makes digital information processing possible, until 1950 this field was called radio technology because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. Today, most electronic devices use semiconductor components to perform electron control and this article focuses on engineering aspects of electronics. Components are generally intended to be connected together, usually by being soldered to a circuit board. Components may be packaged singly, or in more complex groups as integrated circuits, some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active or passive, vacuum tubes were among the earliest electronic components. They were almost solely responsible for the revolution of the first half of the Twentieth Century. They took electronics from parlor tricks and gave us radio, television, phonographs, radar, long distance telephony and they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid state devices have all but completely taken over, vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices. The 608 contained more than 3,000 germanium transistors, thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic, circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types, most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a range of voltage or current as opposed to discrete levels as in digital circuits. The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, one rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance and this type of circuit is usually called mixed signal rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation, an example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit
6.
Diode
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In electronics, a diode is a two-terminal electronic component that conducts primarily in one direction, it has low resistance to the current in one direction, and high resistance in the other. A semiconductor diode, the most common today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. A vacuum tube diode has two electrodes, a plate and a heated cathode, semiconductor diodes were the first semiconductor electronic devices. The discovery of crystals rectifying abilities was made by German physicist Ferdinand Braun in 1874, the first semiconductor diodes, called cats whisker diodes, developed around 1906, were made of mineral crystals such as galena. Today, most diodes are made of silicon, but other such as selenium and germanium are sometimes used. The most common function of a diode is to allow a current to pass in one direction. Thus, the diode can be viewed as a version of a check valve. However, diodes can have complicated behavior than this simple on–off action. Semiconductor diodes begin conducting electricity only if a threshold voltage or cut-in voltage is present in the forward direction. The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature, a semiconductor diodes current–voltage characteristic can be tailored by selecting the semiconductor materials and the doping impurities introduced into the materials during manufacture. These techniques are used to create special-purpose diodes that perform different functions. Tunnel, Gunn and IMPATT diodes exhibit negative resistance, which is useful in microwave, Diodes, both vacuum and semiconductor, can be used as shot-noise generators. Thermionic diodes and solid state diodes were developed separately, at approximately the time, in the early 1900s. Until the 1950s vacuum tube diodes were used frequently in radios because the early point-contact type semiconductor diodes were less stable. In 1873, Frederick Guthrie discovered the principle of operation of thermionic diodes. Guthrie discovered that a positively charged electroscope could be discharged by bringing a piece of white-hot metal close to it. The same did not apply to a negatively charged electroscope, indicating that the current flow was possible in one direction. Thomas Edison independently rediscovered the principle on February 13,1880, at the time, Edison was investigating why the filaments of his carbon-filament light bulbs nearly always burned out at the positive-connected end
7.
Capacitance
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Capacitance is the ability of a body to store an electric charge. There are two related notions of capacitance--self capacitance and mutual capacitance--that are usually both designated by the same term, capacitance. Any object that can be electrically charged exhibits self capacitance, a material with a large self capacitance holds more electric charge at a given voltage, than one with low capacitance. The notion of mutual capacitance is important for understanding the operations of the capacitor. The capacitance is a function only of the geometry of the design, for many dielectric materials, the permittivity and thus the capacitance, is independent of the potential difference between the conductors and the total charge on them. The SI unit of capacitance is the farad, named after the English physicist Michael Faraday, a 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates. In electrical circuits, the capacitance is usually a shorthand for the mutual capacitance between two adjacent conductors, such as the two plates of a capacitor. It is actually mutual capacitance between the turns of the coil and is a form of stray, or parasitic capacitance. This self-capacitance is an important consideration at high frequencies and it changes the impedance of the coil and gives rise to parallel resonance. In many applications this is an effect and sets an upper frequency limit for the correct operation of the circuit. The inverse of capacitance is called elastance, the unit of elastance is the daraf, but is not recognised by SI. A common form is a capacitor, which consists of two conductive plates insulated from each other, usually sandwiching a dielectric material. In a parallel capacitor, capacitance is very nearly proportional to the surface area of the conductor plates. If the charges on the plates are +q and −q, and V gives the voltage between the plates, then the capacitance C is given by C = q V. which gives the voltage/current relationship I = C d V d t. Historically, a farad was regarded as a large unit. Its subdivisions were invariably used, namely the microfarad, nanofarad and picofarad, more recently, technology has advanced such that capacitors of 1 farad and greater can be constructed in a structure little larger than a coin battery. Such capacitors are used for energy storage replacing more traditional batteries. The energy stored in a capacitor is found by integrating the work W, W charging =12 C V2 The discussion above is limited to the case of two conducting plates, although of arbitrary size and shape
8.
Capacitor
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A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance, a capacitor was therefore historically first known as an electric condenser. The physical form and construction of practical capacitors vary widely and many types are in common use. Most capacitors contain at least two electrical conductors often in the form of plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, the nonconducting dielectric acts to increase the capacitors charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, a capacitor does not dissipate energy. No current actually flows through the dielectric, instead, the effect is a displacement of charges through the source circuit, if the condition is maintained sufficiently long, this displacement current through the battery ceases. However, if a voltage is applied across the leads of the capacitor. Capacitance is defined as the ratio of the charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units is the farad, capacitance values of typical capacitors for use in general electronics range from about 1 pF to about 1 mF. The capacitance of a capacitor is proportional to the area of the plates. In practice, the dielectric between the plates passes a small amount of leakage current and it has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance, Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies, in resonant circuits they tune radios to particular frequencies. In electric power systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in digital computers. Von Kleists hand and the water acted as conductors, and the jar as a dielectric, von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine
9.
Voltage-controlled oscillator
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A voltage-controlled oscillator or VCO is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the oscillation frequency. Consequently, modulating signals applied to control input may cause frequency modulation or phase modulation, a VCO may also be part of a phase-locked loop. VCOs can be categorized into two groups based on the type of waveform produced. Linear or harmonic oscillators generate a sinusoidal waveform, harmonic oscillators in electronics usually consist of a resonator with an amplifier that replaces the resonator losses and isolates the resonator from the output. Some examples of harmonic oscillators are LC-tank oscillators and crystal oscillators, in a voltage-controlled oscillator, a voltage input controls the resonant frequency. A varactor diodes capacitance is controlled by the voltage across the diode, consequently, a varactor can be used to change the capacitance of an LC tank. A varactor can also change the resonant frequency of a crystal resonator, relaxation oscillators can generate a sawtooth or triangular waveform. They are commonly used in integrated circuits. They can provide a range of operational frequencies with a minimal number of external components. Relaxation oscillator VCOs can have three topologies, 1) grounded-capacitor VCOs, 2) emitter-coupled VCOs, and 3) delay-based ring VCOs, the first two of these types operate similarly. The time spent in each depends on the rate of charge or discharge of a capacitor. The delay-based ring VCO operates somewhat differently however, for this type, the gain stages are connected in a ring. The output frequency is then a function of the delay in each stage, harmonic oscillator VCOs have these advantages over relaxation oscillators, Frequency stability with respect to temperature, noise, and power supply is much better for harmonic oscillator VCOs. They have good accuracy for frequency control since the frequency is controlled by a crystal or tank circuit, a disadvantage of harmonic oscillator VCOs is that they cannot be easily implemented in monolithic ICs. Relaxation oscillator VCOs are better suited for this technology, relaxation VCOs are also tunable over a wider range of frequencies. A voltage-controlled capacitor is one method of making an LC oscillator vary its frequency in response to a control voltage, any reverse-biased semiconductor diode displays a measure of voltage-dependent capacitance and can be used to change the frequency of an oscillator by varying a control voltage applied to the diode. Special-purpose variable capacitance varactor diodes are available with well-characterized wide-ranging values of capacitance, such devices are very convenient in the manufacture of voltage-controlled oscillators
10.
Parametric oscillator
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A simple example of a parametric oscillator is a child pumping a swing by periodically standing and squatting to increase the size of the swings oscillations. The childs motions vary the moment of inertia of the swing as a pendulum, the pump motions of the child must be at twice the frequency of the swings oscillations. Examples of parameters that may be varied are the resonance frequency ω. Parametric oscillators are used in areas of physics. The classical varactor parametric oscillator consists of a varactor diode connected to a resonant circuit or cavity resonator. It is driven by varying the diodes capacitance by applying a bias voltage. The circuit that varies the diodes capacitance is called the pump or driver, in microwave electronics, waveguide/YAG based parametric oscillators operate in the same fashion. Varactor parametric amplifiers have been developed as low-noise amplifiers in the radio, the advantage of a parametric amplifier is that it has much lower noise than an ordinary amplifier based on a gain device like a transistor or vacuum tube. This is because in the amplifier an reactance is varied instead of a resistance. They have been used in very low noise radio receivers in radio telescopes, Parametric resonance occurs in a mechanical system when a system is parametrically excited and oscillates at one of its resonant frequencies. Parametric excitation differs from forcing since the action appears as a time varying modification on a system parameter, michael Faraday was the first to notice oscillations of one frequency being excited by forces of double the frequency, in the crispations observed in a wine glass excited to sing. Franz Melde generated parametric oscillations in a string by employing a tuning fork to periodically vary the tension at twice the frequency of the string. Parametric oscillation was first treated as a phenomenon by Rayleigh. Parametric amplifiers were first used in 1913-1915 for radio telephony from Berlin to Vienna and Moscow, the early paramps varied inductances, but other methods have been developed since, e. g. the varactor diodes, klystron tubes, Josephson junctions and optical methods. D2 x d t 2 + β d x d t + ω2 x =0 This equation is linear in x, by assumption, the parameters ω2 and β depend only on time and do not depend on the state of the oscillator. In general, β and/or ω2 are assumed to vary periodically, without a compensating energy-loss mechanism provided by β, the oscillation amplitude grows exponentially. A familiar experience of both parametric and driven oscillation is playing on a swing and this changes moment of inertia of the swing and hence the resonance frequency, and children can quickly reach large amplitudes provided that they have some amplitude to start with. Standing and squatting at rest, however, leads nowhere and we begin by making a change of variables q = d e f e D x where D is a time integral of the damping D = d e f 12 ∫ t d τ β
11.
Frequency modulation
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In telecommunications and signal processing, frequency modulation is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. This contrasts with amplitude modulation, in which the amplitude of the wave varies. This modulation technique is known as frequency-shift keying, FSK is widely used in modems and fax modems, and can also be used to send Morse code. Frequency modulation is used for FM radio broadcasting. For this reason, most music is broadcast over FM radio, frequency modulation has a close relationship with phase modulation, phase modulation is often used as an intermediate step to achieve frequency modulation. Mathematically both of these are considered a case of quadrature amplitude modulation. While most of the energy of the signal is contained within fc ± fΔ, the frequency spectrum of an actual FM signal has components extending infinitely, although their amplitude decreases and higher-order components are often neglected in practical design problems. Mathematically, a baseband modulated signal may be approximated by a continuous wave signal with a frequency fm. This method is also named as Single-tone Modulation. As in other systems, the modulation index indicates by how much the modulated variable varies around its unmodulated level. e. The maximum deviation of the frequency from the carrier frequency. For a sine wave modulation, the index is seen to be the ratio of the peak frequency deviation of the carrier wave to the frequency of the modulating sine wave. If h ≪1, the modulation is called narrowband FM, sometimes modulation index h<0.3 rad is considered as Narrowband FM otherwise Wideband FM. In the case of digital modulation, the carrier f c is never transmitted, rather, one of two frequencies is transmitted, either f c + Δ f or f c − Δ f, depending on the binary state 0 or 1 of the modulation signal. If h ≫1, the modulation is called wideband FM, if the frequency deviation is held constant and the modulation frequency increased, the spacing between spectra increases. The carrier and sideband amplitudes are illustrated for different modulation indices of FM signals, for particular values of the modulation index, the carrier amplitude becomes zero and all the signal power is in the sidebands. Since the sidebands are on sides of the carrier, their count is doubled, and then multiplied by the modulating frequency to find the bandwidth. For example,3 kHz deviation modulated by a 2.2 kHz audio tone produces an index of 1.36. Suppose that we limit ourselves to only those sidebands that have an amplitude of at least 0.01
12.
Phase-locked loop
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A phase-locked loop or phase lock loop abbreviated as PLL is a control system that generates an output signal whose phase is related to the phase of an input signal. While there are several differing types, it is easy to visualize as an electronic circuit consisting of a variable frequency oscillator. The oscillator generates a signal, and the phase detector compares the phase of that signal with the phase of the input periodic signal. Bringing the output signal back toward the signal for comparison is called a feedback loop since the output is fed back toward the input forming a loop. Keeping the input and output phase in lock step also implies keeping the input and output frequencies the same, consequently, in addition to synchronizing signals, a phase-locked loop can track an input frequency, or it can generate a frequency that is a multiple of the input frequency. These properties are used for clock synchronization, demodulation. Phase-locked loops are widely employed in radio, telecommunications, computers, for a practical idea of what is going on, consider an auto race. There are many cars, and the driver of each of them wants to go around the track as fast as possible, each lap corresponds to a complete cycle, and each car will complete dozens of laps per hour. The number of laps per hour corresponds to an angular velocity, but the number of laps corresponds to a phase. During most of the race, each car is on its own and the driver of the car is trying to beat the driver of other car on the course. However, if there is an accident, a car comes out to set a safe speed. None of the cars are permitted to pass the pace car. While it is on the track, the car is a reference. Each driver will measure the difference between him and the pace car. If the driver is far away, he will increase his speed to close the gap. If hes too close to the car, he will slow down. The result is all the race cars lock on to the phase of the pace car, the cars travel around the track in a tight group that is a small fraction of a lap. Phase can be proportional to time, so a difference can be a time difference
13.
Frequency synthesizer
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A frequency synthesizer is an electronic circuit for generating any of a range of frequencies from a single fixed timebase or oscillator. Three types of synthesizer can be distinguished, the first and second type are routinely found as stand-alone architecture, direct analog synthesis and the more modern direct digital synthesizer. The third type are used as communication system IC building-blocks. It is in ways similar to a DDS, but it has architectural differences. One of its big advantages is to allow a finer resolution than other types of synthesizers with a given reference frequency. Automatic frequency control solves some of the problem, but manual retuning was often necessary. Since transmitter frequencies are stabilized, a source of fixed. Quartz crystal resonators are many orders of more stable than LC circuits. However the resonant frequency of a crystal is determined by its dimensions, one solution is to employ many crystals, one for each frequency desired, and switch the correct one into the circuit. This brute force technique is practical when only a handful of frequencies are required, for example, the FM radio band in many countries supports 100 individual channel frequencies from about 88 MHz to 108 MHz, the ability to tune in each channel would require 100 crystals. Cable television can support even more frequencies or channels over a wider band. A large number of crystals increases cost and requires greater space, the solution to this was the development of circuits which could generate multiple frequencies from a reference frequency produced by a crystal oscillator. This is called a frequency synthesizer, the new synthesized frequencies would have the frequency stability of the master crystal oscillator, since they were derived from it. Many techniques have been devised over the years for synthesizing frequencies, some approaches include phase locked loops, double mix, triple mix, harmonic, double mix divide, and direct digital synthesis. The choice of approach depends on several factors, such as cost, complexity, frequency step size, switching rate, phase noise, coherent techniques generate frequencies derived from a single, stable master oscillator. In most applications, an oscillator is common, but other resonators. Incoherent techniques derive frequencies from a set of several stable oscillators, the vast majority of synthesizers in commercial applications use coherent techniques due to simplicity and low cost. Synthesizers used in radio receivers are largely based on phase-locked loops or PLLs
14.
Television set
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A television set, more commonly called a television, TV, TV set, television receiver, or telly, is a device that combines a tuner, display, and loudspeakers for the purpose of viewing television. Introduced in the late 1920s in mechanical form, television became a popular consumer product after World War II in electronic form. The addition of color to broadcast television after 1953 further increased the popularity of television sets in the 1960s, the ubiquitous television set became the display device for the first recorded media in the 1970s, such as Betamax, VHS and later DVD. It was also the display device for the first generation of home computers, in the 2010s flat panel television incorporating liquid-crystal displays, especially LED-backlit LCDs, largely replaced cathode ray tubes and other displays. Modern flat panel TVs are typically capable of display and can also play content from a USB device. Mechanical televisions were sold from 1928 to 1934 in the United Kingdom, United States. The Baird Televisor is considered the first mass-produced television, selling about a thousand units, the first commercially made electronic televisions with cathode ray tubes were manufactured by Telefunken in Germany in 1934, followed by other makers in France, Britain, and America. The cheapest model with a 12-inch screen was $445, an estimated 19,000 electronic televisions were manufactured in Britain, and about 1,600 in Germany, before World War II. About 7, 000–8,000 electronic sets were made in the U. S. before the War Production Board halted manufacture in April 1942, production resuming in August 1945. While only 0. 5% of U. S. households had a television in 1946,55. 7% had one in 1954, and 90% by 1962. In Britain, there were 15,000 television households in 1947,1.4 million in 1952, by the late 1960s and early 1970s, color television had come into wide use. In Britain, BBC1, BBC2 and ITV were regularly broadcasting in colour by 1969, during the first decade of the 21st century, CRT picture tube display technology was almost entirely supplanted worldwide by flat panel displays. By the early 2010s, LCD TVs, which increasingly used LED-backlit LCDs, television sets may employ one of several available display technologies. The production of plasma and CRT displays has been almost completely discontinued, the cathode ray tube is a vacuum tube containing one or more electron guns and a fluorescent screen used to view images. It has a means to accelerate and deflect the beam onto the screen to create the images. The images may represent electrical waveforms, pictures, radar targets or others, the CRT uses an evacuated glass envelope which is large, deep, fairly heavy, and relatively fragile. As a matter of safety, the face is made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions. In television sets and computer monitors, the front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster
15.
Mobile phone
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A mobile phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the systems of a mobile phone operator. Most modern mobile telephone services use a network architecture, and, therefore. Mobile phones which offer these and more general computing capabilities are referred to as smartphones, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. In 1983, the DynaTAC 8000x was the first commercially available mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to seven billion, penetrating 100% of the global population. In first quarter of 2016, the top smartphone manufacturers were Samsung, Apple, a handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a pocket-size folding telephone with a thin carbon microphone. Early predecessors of cellular phones included analog radio communications from ships, the race to create truly portable telephone devices began after World War II, with developments taking place in many countries. These 0G systems were not cellular, supported few simultaneous calls, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. The first commercial automated cellular network was launched in Japan by Nippon Telegraph and this was followed in 1981 by the simultaneous launch of the Nordic Mobile Telephone system in Denmark, Finland, Norway, and Sweden. Several other countries followed in the early to mid-1980s. These first-generation systems could support far more simultaneous calls but still used analog cellular technology, in 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. In 1991, the digital cellular technology was launched in Finland by Radiolinja on the GSM standard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators, ten years later, in 2001, the third generation was launched in Japan by NTT DoCoMo on the WCDMA standard. This was followed by 3. 5G, 3G+ or turbo 3G enhancements based on the high-speed packet access family, allowing UMTS networks to have data transfer speeds. By 2009, it had become clear that, at point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications. Consequently, the industry began looking to data-optimized fourth-generation technologies, with the promise of speed improvements up to ten-fold over existing 3G technologies
16.
Electron hole
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In physics, chemistry, and electronic engineering, an electron hole is the lack of an electron at a position where one could exist in an atom or atomic lattice. Holes in a crystal lattice can move through the lattice as electrons can. They play an important role in the operation of devices such as transistors, diodes. However they are not actually particles, but rather quasiparticles, they are different from the positron, if an electron is excited into a higher state it leaves a hole in its old state. This meaning is used in Auger electron spectroscopy, in computational chemistry, in crystals, electronic band structure calculations lead to an effective mass for the electrons, which typically is negative at the top of a band. The negative mass is a concept, and in these situations a more familiar picture is found by considering a positive charge with a positive mass. In solid-state physics, a hole is the absence of an electron from a full valence band. A hole is essentially a way to conceptualize the interactions of the electrons within a full system. In some ways, the behavior of a hole within a crystal lattice is comparable to that of the bubble in a full bottle of water. Hole conduction in a band can be explained by the following analogy. Imagine a row of people seated in an auditorium, where there are no spare chairs, someone in the middle of the row wants to leave, so he jumps over the back of the seat into an empty row, and walks out. The empty row is analogous to the band, and the person walking out is analogous to a free electron. Now imagine someone else comes along and wants to sit down, the empty row has a poor view, so he does not want to sit there. Instead, a person in the crowded row moves into the empty seat the first person left behind, the empty seat moves one spot closer to the edge and the person waiting to sit down. The next person follows, and the next, et cetera, one could say that the empty seat moves towards the edge of the row. Once the empty seat reaches the edge, the new person can sit down, in the process everyone in the row has moved along. If those people were charged, this movement would constitute conduction. If the seats themselves were positively charged, then only the vacant seat would be positive and this is a very simple model of how hole conduction works
17.
Depletion region
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The only elements left in the depletion region are ionized donor or acceptor impurities. The depletion region is so named because it is formed from a region by removal of all free charge carriers. The following discussion is limited to the p–n junction and the MOS capacitor, a depletion region forms instantaneously across a p–n junction. Electrons and holes diffuse into regions with lower concentrations of electrons and holes, by definition, N-type semiconductor has an excess of free electrons compared to the P-type region, and P-type has an excess of holes compared to the N-type region. Therefore, when N-doped and P-doped pieces of semiconductor are placed together to form a junction, electrons migrate into the P-side and holes migrate into the N-side. Departure of an electron from the N-side to the P-side leaves a positive donor ion behind on the N-side, following transfer, the diffused electrons come into contact with holes on the P-side and are eliminated by recombination. Likewise for the holes on the N-side. The net result is the electrons and holes are gone. The uncompensated ions are positive on the N side and negative on the P side and this creates an electric field that provides a force opposing the continued exchange of charge carriers. When the electric field is sufficient to arrest further transfer of holes and electrons, integrating the electric field across the depletion region determines what is called the built-in voltage. Mathematically speaking, charge transfer in semiconductor devices is due both to conduction driven by the field and by diffusion. Conduction forces the holes along the direction of the electric field, diffusion moves the carriers in the direction of decreasing concentration, so for holes a negative current results for a positive density gradient. When the two current components balance, as in the depletion region at dynamic equilibrium, the current is zero due to the Einstein relation. Forward bias narrows the depletion region and lowers the barrier to carrier injection, in more detail, majority carriers get some energy from the bias field, enabling them to go into the region and neutralize opposite charges. The more bias the more neutralization occurs, the carriers can be recombined to the ions but thermal energy immediately makes recombined carriers transition back as Fermi energy is in proximity. When bias is strong enough that the region becomes very thin, the diffusion component of the current greatly increases. In this case the net current is rightward in the figure of the p–n junction, the carrier density is large, making the junction conductive and allowing a large forward current. The mathematical description of the current is provided by the Shockley diode equation, the low current conducted under reverse bias and the large current under forward bias is an example of rectification
18.
Square root
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In mathematics, a square root of a number a is a number y such that y2 = a, in other words, a number y whose square is a. For example,4 and −4 are square roots of 16 because 42 =2 =16, every nonnegative real number a has a unique nonnegative square root, called the principal square root, which is denoted by √a, where √ is called the radical sign or radix. For example, the square root of 9 is 3, denoted √9 =3. The term whose root is being considered is known as the radicand, the radicand is the number or expression underneath the radical sign, in this example 9. Every positive number a has two roots, √a, which is positive, and −√a, which is negative. Together, these two roots are denoted ± √a, although the principal square root of a positive number is only one of its two square roots, the designation the square root is often used to refer to the principal square root. For positive a, the square root can also be written in exponent notation. Square roots of numbers can be discussed within the framework of complex numbers. In Ancient India, the knowledge of theoretical and applied aspects of square and square root was at least as old as the Sulba Sutras, a method for finding very good approximations to the square roots of 2 and 3 are given in the Baudhayana Sulba Sutra. Aryabhata in the Aryabhatiya, has given a method for finding the root of numbers having many digits. It was known to the ancient Greeks that square roots of positive numbers that are not perfect squares are always irrational numbers, numbers not expressible as a ratio of two integers. This is the theorem Euclid X,9 almost certainly due to Theaetetus dating back to circa 380 BC, the particular case √2 is assumed to date back earlier to the Pythagoreans and is traditionally attributed to Hippasus. Mahāvīra, a 9th-century Indian mathematician, was the first to state that square roots of negative numbers do not exist, a symbol for square roots, written as an elaborate R, was invented by Regiomontanus. An R was also used for Radix to indicate square roots in Gerolamo Cardanos Ars Magna, according to historian of mathematics D. E. Smith, Aryabhatas method for finding the root was first introduced in Europe by Cataneo in 1546. According to Jeffrey A. Oaks, Arabs used the letter jīm/ĝīm, the letter jīm resembles the present square root shape. Its usage goes as far as the end of the century in the works of the Moroccan mathematician Ibn al-Yasamin. The symbol √ for the root was first used in print in 1525 in Christoph Rudolffs Coss
19.
MOSFET
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The metal–oxide–semiconductor field-effect transistor is a type of field-effect transistor. It has a gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals, although FET is sometimes used when referring to MOSFET devices, other types of field-effect transistors also exist. Because these two terminals are connected to each other internally, only three terminals appear in electrical diagrams. The basic principle of the transistor was first patented by Julius Edgar Lilienfeld in 1925. The main advantage of a MOSFET over a regular transistor is that it very little current to turn on. In enhancement mode MOSFETs, a voltage drop across the oxide induces a conducting channel between the source and drain contacts via the field effect. The term enhancement mode refers to the increase of conductivity with increase in oxide field that adds carriers to the channel, also referred to as the inversion layer. The channel can contain electrons, or holes, opposite in type to the substrate, so nMOS is made with a p-type substrate, the metal in the name MOSFET is now often a misnomer because the previously metal gate material is now often a layer of polysilicon. Aluminium had been the material until the mid-1970s, when polysilicon became dominant. Metallic gates are regaining popularity, since it is difficult to increase the speed of operation of transistors without metal gates, likewise, the oxide in the name can be a misnomer, as different dielectric materials are used with the aim of obtaining strong channels with smaller applied voltages. An insulated-gate field-effect transistor or IGFET is a term almost synonymous with MOSFET. The term may be inclusive, since many MOSFETs use a gate that is not metal. Another synonym is MISFET for metal–insulator–semiconductor FET, the MOSFET is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925. Twenty five years later, when Bell Telephone attempted to patent the junction transistor, they found Lilienfeld already holding a patent, Bell Labs was able to work out an agreement with Lilienfeld, who was still alive at that time. It was at time the Bell Labs version was given the name bipolar junction transistor, or simply junction transistor. In 1959, Dawon Kahng and Martin M. Atalla at Bell Labs invented the metal–oxide–semiconductor field-effect transistor as an offshoot to the patented FET design and it used crystalline silicon for the semiconductor and a thermally oxidized layer of silicon dioxide for the insulator
20.
Schottky diode
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The Schottky diode, also known as hot carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low voltage drop and a very fast switching action. The cats-whisker detectors used in the days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes. When sufficient forward voltage is applied, a current flows in the forward direction, a silicon diode has a typical forward voltage of 600–700 mV, while the Schottkys forward voltage is 150 –450 mV. This lower forward voltage requirement allows higher switching speeds and better system efficiency, a metal–semiconductor junction is formed between a metal and a semiconductor, creating a Schottky barrier. Typical metals used are molybdenum, platinum, chromium or tungsten, the metal side acts as the anode, and n-type semiconductor acts as the cathode of the diode. This Schottky barrier results in very fast switching and low forward voltage drop. The choice of the combination of the metal and semiconductor determines the voltage of the diode. Both n- and p-type semiconductors can develop Schottky barriers, however, the p-type typically has a much lower forward voltage. With increased doping of the semiconductor, the width of the depletion region drops, below a certain width, the charge carriers can tunnel through the depletion region. At very high doping levels, the junction does not behave as a rectifier anymore, as the edges of the Schottky contact are fairly sharp, a high electric field gradient occurs around them, which limits how large the reverse breakdown voltage threshold can be. Various strategies are used, from guard rings to overlaps of metallization to spread out the field gradient, the guard rings consume valuable die area and are used primarily for larger higher-voltage diodes, while overlapping metallization is employed primarily with smaller low-voltage diodes. Schottky diodes are used as antisaturation clamps in Schottky transistors. Schottky diodes made from palladium silicide are excellent due to their forward voltage. The Schottky temperature coefficient is lower than the coefficient of the B–C junction, for power Schottky diodes, the parasitic resistances of the buried n+ layer and the epitaxial n-type layer become important. The resistance of the layer is more important than it is for a transistor. However, it serves as a distributed ballasting resistor over the area of the junction and, under usual conditions. In comparison with the power p–n diodes the Schottky diodes are less rugged, the relative advantage of the lower forward voltage of Schottky diodes is diminished at higher forward currents, where the voltage drop is dominated by the series resistance
21.
CMOS
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Complementary metal–oxide–semiconductor, abbreviated as CMOS /ˈsiːmɒs/, is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, CMOS technology is also used for several analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. In 1963, while working for Fairchild Semiconductor, Frank Wanlass patented CMOS, CMOS is also sometimes referred to as complementary-symmetry metal–oxide–semiconductor. Two important characteristics of CMOS devices are high noise immunity and low power consumption. Since one transistor of the pair is always off, the series combination draws significant power only momentarily during switching between on and off states, CMOS also allows a high density of logic functions on a chip. It was primarily for this reason that CMOS became the most used technology to be implemented in VLSI chips, aluminium was once used but now the material is polysilicon. Other metal gates have made a comeback with the advent of high-k dielectric materials in the CMOS process, as announced by IBM and Intel for the 45 nanometer node and beyond. CMOS refers to both a style of digital circuitry design and the family of processes used to implement that circuitry on integrated circuits. CMOS circuitry dissipates less power than logic families with resistive loads, since this advantage has increased and grown more important, CMOS processes and variants have come to dominate, thus the vast majority of modern integrated circuit manufacturing is on CMOS processes. As of 2010, CPUs with the best performance per watt each year have been CMOS static logic since 1976, CMOS circuits use a combination of p-type and n-type metal–oxide–semiconductor field-effect transistor to implement logic gates and other digital circuits. CMOS always uses all enhancement-mode MOSFETs, CMOS circuits are constructed in such a way that all PMOS transistors must have either an input from the voltage source or from another PMOS transistor. Similarly, all NMOS transistors must have either an input from ground or from another NMOS transistor, the composition of a PMOS transistor creates low resistance between its source and drain contacts when a low gate voltage is applied and high resistance when a high gate voltage is applied. On the other hand, the composition of an NMOS transistor creates high resistance between source and drain when a low voltage is applied and low resistance when a high gate voltage is applied. CMOS accomplishes current reduction by complementing every nMOSFET with a pMOSFET, a high voltage on the gates will cause the nMOSFET to conduct and the pMOSFET to not conduct, while a low voltage on the gates causes the reverse. This arrangement greatly reduces power consumption and heat generation, however, during the switching time, both MOSFETs conduct briefly as the gate voltage goes from one state to another. This induces a brief spike in consumption and becomes a serious issue at high frequencies. The image on the right shows what happens when an input is connected to both a PMOS transistor and an NMOS transistor, when the voltage of input A is low, the NMOS transistors channel is in a high resistance state. This limits the current that can flow from Q to ground, the PMOS transistors channel is in a low resistance state and much more current can flow from the supply to the output
22.
Monolithic microwave integrated circuit
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A Monolithic Microwave Integrated Circuit, or MMIC, is a type of integrated circuit device that operates at microwave frequencies. These devices typically perform functions such as mixing, power amplification, low-noise amplification. Inputs and outputs on MMIC devices are matched to a characteristic impedance of 50 ohms. This makes them easier to use, as cascading of MMICs does not then require a matching network. Additionally, most microwave test equipment is designed to operate in a 50-ohm environment, MMICs are dimensionally small and can be mass-produced, which has allowed the proliferation of high-frequency devices such as cellular phones. MMICs were originally fabricated using gallium arsenide, a III-V compound semiconductor and it has two fundamental advantages over silicon, the traditional material for IC realisation, device speed and a semi-insulating substrate. Both factors help with the design of high-frequency circuit functions, however, the speed of Si-based technologies has gradually increased as transistor feature sizes have reduced, and MMICs can now also be fabricated in Si technology. The primary advantage of Si technology is its lower fabrication cost compared with GaAs, silicon wafer diameters are larger and the wafer costs are lower, contributing to a less expensive IC. Originally, MMICs used MEtal-Semiconductor Field-Effect Transistors as the active device, more recently High Electron Mobility Transistors, Pseudomorphic HEMTs and Heterojunction Bipolar Transistors have become common. Other III-V technologies, such as indium phosphide, have shown to offer superior performance to GaAs in terms of gain, higher cutoff frequency. However they also tend to be expensive due to smaller wafer sizes. Silicon germanium is a Si-based compound semiconductor technology offering higher-speed transistors than conventional Si devices, gallium nitride is also an option for MMICs. Because GaN transistors can operate at higher temperatures and work at much higher voltages than GaAs transistors. Integrated circuit Hybrid integrated circuit Transmission line MESFET High-electron-mobility transistor HBT Practical MMIC Design published by Artech House ISBN 1-59693-036-5 Author S. P
23.
LC circuit
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The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuits resonant frequency. LC circuits are used either for generating signals at a particular frequency and they are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers. An LC circuit is a model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components, the purpose of an LC circuit is usually to oscillate with minimal damping, so the resistance is made as low as possible. While no practical circuit is without losses, it is instructive to study this ideal form of the circuit to gain understanding. For a circuit model incorporating resistance, see RLC circuit, the two-element LC circuit described above is the simplest type of inductor-capacitor network. It is also referred to as a second order LC circuit to distinguish it more complicated LC networks with more inductors and capacitors. Such LC networks with more than two reactances may have more than one resonant frequency, the order of the network is the order of the rational function describing the network in the complex frequency variable s. Generally, the order is equal to the number of L and C elements in the circuit, an LC circuit, oscillating at its natural resonant frequency, can store electrical energy. A capacitor stores energy in the field between its plates, depending on the voltage across it, and an inductor stores energy in its magnetic field. If an inductor is connected across a capacitor, current will start to flow through the inductor, building up a magnetic field around it. Eventually all the charge on the capacitor will be gone and the voltage across it will reach zero, however, the current will continue, because inductors resist changes in current. The current will begin to charge the capacitor with a voltage of opposite polarity to its original charge. Due to Faradays law, the EMF which drives the current is caused by a decrease in the magnetic field, when the magnetic field is completely dissipated the current will stop and the charge will again be stored in the capacitor, with the opposite polarity as before. Then the cycle will begin again, with the current flowing in the direction through the inductor. The charge flows back and forth between the plates of the capacitor, through the inductor, the energy oscillates back and forth between the capacitor and the inductor until internal resistance makes the oscillations die out. In most applications the tuned circuit is part of a circuit which applies alternating current to it. If the frequency of the current is the circuits natural resonant frequency
24.
2N2222
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The 2N2222 is a common NPN bipolar junction transistor used for general purpose low-power amplifying or switching applications. It is designed for low to medium current, low power, medium voltage and it was originally made in the TO-18 metal can as shown in the picture. The 2N2222 is considered a very common transistor, and is used as an exemplar of an NPN transistor and it is frequently used as a small-signal transistor, and it remains a small general purpose transistor of enduring popularity. The 2N2222 was part of a family of devices described by Motorola at a 1962 IRE convention, since then it has been made by many semiconductor companies, for example, Texas Instruments. The JEDEC registration of a device number ensures particular rated values will be met by all parts offered under that number, other part numbers will have different parameters. The exact specifications depend on the manufacturer, case type, therefore, it is important to refer to the datasheet for the exact part number and manufacturer. All variations have a beta or current gain of at least 100 in optimal conditions and it is used in a variety of analog amplification and switching applications. NPN silicon transistors with similar properties are also made in a variety of small through-hole and surface mount packages including TO-92, SOT-23, and SOT-223. The P2N2222 has a different order of pins than the metal case 2N2222, with its emitter and collector connections switched, the general specifications of the various variants are similar, with the biggest difference being the maximum allowable current and power dissipation. The BC548 is a low voltage, low current, general-purpose switching transistor in a TO-92 package, the 2N2907 is an equally popular PNP transistor complementary to the 2N2222. The 2N3904 is an NPN transistor that can only switch one-third the current of the 2N2222 but has similar characteristics. The 2N3904 exhibits its forward gain peak at a lower current than the 2N2222, the 2N2219 is very similar with higher power dissipation rating. The 2N2222 and 2N2907 are complementary transistor pairs
25.
BC548
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The BC548 is a general-purpose NPN bipolar junction transistor commonly used in European and American electronic equipment. It is notably often the first type of bipolar transistor hobbyists encounter, the BC548 is low in cost and widely available. The BC548 is a part of a higher-quality family of NPN and this series, introduced in 1966 by Philips, became the most used transistors in Australia and was taken up by many European manufacturers. Datasheets for the BC548 give specifications that are identical to, or exceed, thus the BC548 is a valid substitute in any circuit designed for the older BC108, which includes many Mullard and Philips published designs. As of 2016, the BC548 is principally produced by ON Semiconductor, the BC548 is supplied in a standard TO-92 3-pin package. The assignment of transistor elements to leads, i. e. the pinout, uses the convention used by some -. As viewed in the image, going from left to right, the pinout is as follows, lead 1 is the collector, lead 2 is the base. Sometimes the middle pin is supplied bent to form a triangle of leads to match the pinout of the BC108 more exactly, the BC548 part number is assigned by Pro Electron, which allows many manufacturers to offer electrically and physically interchangeable parts under one identification. The BC556 to BC560 are the PNP counterparts of the BC546 to BC550, see the BC108 family for a table of these differences, and comparisons with predecessor types. The power rating is also subject to variation, from 500mW to 625mW, there is lot of variation in the ft-transition maximum frequency from manufacturer to manufacturer. The type number of any of the devices in this family may be followed by a letter, A to C, the BC548 is available in three different gain groups. Notes, Some manufacturers place slightly different limits on the gain groups, the BC547 variant rarely is available in the C gain group, and the BC549 rarely in the A gain group. The PNP counterparts of the BC546 to BC550 are the BC556 to BC560 respectively, the surface-mount package versions are the BC846 to BC850. 2N2222, 2N2907 2N3904, 2N3906 2N3055 BC108 KT315
26.
1N400x general-purpose diodes
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The 1N4001 series is a family of popular 1 A general-purpose silicon rectifier diodes commonly used in AC adapters for common household appliances. Blocking voltage varies from 50 to 1000 volts and this diode series is available in DO-41 axial package, SMA and MELF surface mount packages. The 1N5400 series is a popular series for higher-current 3 A applications. These diodes are available in the larger DO-201AD axial package to dissipate heat better. These are fairly low-speed rectifier diodes, being inefficient for square waves of more than 15 kHz and these devices are widely used and recommended. The series was sourced by many manufacturers. The 1N4000 series were in the Motorola Semiconductor Data Manual in 1965, the 1N5400 series were announced in Electrical Design News in 1968, along with the now lesser known 1.5 A 1N5391 series. The table below shows the maximum repetitive reverse blocking voltages of each of the members of the 1N4000 and 1N5400 series, in the version of these components manufactured for Fairchild Semiconductor in Suzhou, the silicon chip that rectifies the current weighs just 880 micrograms
27.
Q factor
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Higher Q indicates a lower rate of energy loss relative to the stored energy of the resonator, the oscillations die out more slowly. A pendulum suspended from a high-quality bearing, oscillating in air, has a high Q, resonators with high quality factors have low damping so that they ring or vibrate longer. High-Q oscillators oscillate with a range of frequencies and are more stable. The quality factor of oscillators varies substantially from system to system, systems for which damping is important have Q near 1⁄2. Clocks, lasers, and other resonating systems that need either strong resonance or high frequency stability have high quality factors, tuning forks have quality factors around 1000. The quality factor of atomic clocks, superconducting RF cavities used in accelerators, there are many alternative quantities used by physicists and engineers to describe how damped an oscillator is. Important examples include, the ratio, relative bandwidth, linewidth and bandwidth measured in octaves. The concept of Q originated with K. S. Johnson of Western Electric Companys Engineering Department while evaluating the quality of coils and his choice of the symbol Q was only because, at the time, all other letters of the alphabet were taken. The term was not intended as an abbreviation for quality or quality factor, in the context of resonators, there are two common definitions for Q, which arent necessarily equivalent. They become approximately equivalent as Q becomes larger, meaning the resonator becomes less damped. e. The bandwidth over which the power of vibration is greater than half the power at the resonant frequency, ωr = 2πfr is the resonant frequency. The factor 2π makes Q expressible in terms, involving only the coefficients of the second-order differential equation describing most resonant systems. In electrical systems, the energy is the sum of energies stored in lossless inductors and capacitors. This definition is consistent with its usage in describing circuits with a single reactive element, the Q factor determines the qualitative behavior of simple damped oscillators. A system with low quality factor is said to be overdamped, such a system doesnt oscillate at all, but when displaced from its equilibrium steady-state output it returns to it by exponential decay, approaching the steady state value asymptotically. It has a response that is the sum of two decaying exponential functions with different rates of decay. As the quality factor decreases the slower decay mode becomes stronger relative to the faster mode, a second-order low-pass filter with a very low quality factor has a nearly first-order step response, the systems output responds to a step input by slowly rising toward an asymptote. A system with high quality factor is said to be underdamped, underdamped systems combine oscillation at a specific frequency with a decay of the amplitude of the signal
28.
Variable capacitor
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A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are used in L/C circuits to set the resonance frequency, e. g. to tune a radio, or as a variable reactance. In mechanically controlled variable capacitors, the distance between the plates, or the amount of surface area which overlaps, can be changed. Air or plastic foils can be used as dielectric material, by choosing the shape of the rotary plates, various functions of capacitance vs. angle can be created, e. g. to obtain a linear frequency scale. Various forms of reduction gear mechanisms are used to achieve finer tuning control, i. e. to spread the variation of capacity over a larger angle. Measurement of the capacitance of a rotary capacitor A vacuum variable capacitor uses a set of made from concentric cylinders that can be slid in or out of an opposing set of cylinders. These plates are sealed inside of a non-conductive envelope such as glass or ceramic. The movable part is mounted on a flexible membrane that seals. A screw shaft is attached to the plunger, when the shaft is turned the plunger moves in or out of the sleeve, the vacuum not only increases the working voltage and current handling capacity of the capacitor it also greatly reduces the chance of arcing across the plates. The most common usage for vacuum variables are in high powered transmitters such as used for broadcasting, military. Very cheap variable capacitors are constructed from layered aluminium and plastic foils that are pressed together using a screw. These so-called squeezers can’t provide a stable and reproducible capacitance, however, a variant of this structure that allows for linear movement of one set of plates to change the plate overlap area is also used and might be called a slider. This has practical advantages for makeshift or home construction and may be found in resonant loop antennas or crystal radios, small variable capacitors operated by screwdriver are called trimmer capacitors. In addition to air and plastic, trimmers can also be using a ceramic dielectric. Capacitors with multiple sections often include trimmer capacitors in parallel to the variable sections, since the peak RF current normally flows from one stator to the other without going through wiper contacts, butterfly capacitors can handle large resonance RF currents, e. g. in magnetic loop antennas. The closely related split stator variable capacitor does not have the limitation of 90° angle since it uses two separate packs of rotor electrodes arranged axially behind one another. Unlike in a capacitor with several sections, the plates in a split stator capacitor are mounted on opposite sides of the rotor axis. Differential variable capacitors can therefore be used in capacitive potentiometric circuits, the variable capacitor with air dielectric was invented by the Hungarian engineer Dezső Korda
29.
Saturable reactor
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A saturable reactor in electrical engineering is a special form of inductor where the magnetic core can be deliberately saturated by a direct electric current in a control winding. Once saturated, the inductance of the saturable reactor drops dramatically and this decreases inductive reactance and allows increased flow of the AC current. In addition, because of the arrangement of the power windings, the control winding, and the core. The AC power windings are also usually configured so that they cancel out AC voltages that would otherwise be induced into the control winding, in this way, the required magnitude of the control current can be also held roughly constant, no matter what the load. Magnetic amplifier Constant voltage transformer Choudhury, D. Roy
30.
Spectrum analyzer
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A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals, optical spectrum analyzers also exist, which use direct optical techniques such as a monochromator to make measurements. These parameters are useful in the characterization of electronic devices, such as wireless transmitters, the display of a spectrum analyzer has frequency on the horizontal axis and the amplitude displayed on the vertical axis. To the casual observer, a spectrum analyzer looks like an oscilloscope and, in fact, the first spectrum analyzers, in the 1960s, were swept-tuned instruments. Following the discovery of the fast Fourier transform in 1965, the first FFT-based analyzers were introduced in 1967, today, there are three basic types of analyzer, the swept-tuned spectrum analyzer, the vector signal analyzer, and the real-time spectrum analyzer. Spectrum analyzer types are distinguished by the used to obtain the spectrum of a signal. By sweeping the receivers center-frequency through a range of frequencies, the output is also a function of frequency, but while the sweep centers on any particular frequency, it may be missing short-duration events at other frequencies. An FFT analyzer computes a time-sequence of periodograms, FFT refers to a particular mathematical algorithm used in the process. This is commonly used in conjunction with a receiver and analog-to-digital converter, as above, the receiver reduces the center-frequency of a portion of the input signal spectrum, but the portion is not swept. The purpose of the receiver is to reduce the rate that the analyzer must contend with. With a sufficiently low sample-rate, FFT analyzers can process all the samples, Spectrum analyzers tend to fall into four form factors, benchtop, portable, handheld and networked. This form factor is useful for applications where the spectrum analyzer can be plugged into AC power, bench top spectrum analyzers have historically offered better performance and specifications than the portable or handheld form factor. Bench top spectrum analyzers normally have multiple fans to dissipate heat produced by the processor, due to their architecture, bench top spectrum analyzers typically weigh more than 30 pounds. Some bench top spectrum analyzers offer optional battery packs, allowing them to be used away from AC power and this type of analyzer is often referred to as a portable spectrum analyzer. This form factor is useful for any applications where the spectrum analyzer needs to be taken outside to make measurements or simply carried while in use, attributes that contribute to a useful portable spectrum analyzer include, Optional battery-powered operation to allow the user to move freely outside. Clearly viewable display to allow the screen to be read in bright sunlight and this form factor is useful for any application where the spectrum analyzer needs to be very light and small. Handheld analyzers usually offer a limited capability relative to larger systems, attributes that contribute to a useful handheld spectrum analyzer include, Very low power consumption. Battery-powered operation while in the field to allow the user to move freely outside and this form factor does not include a display and these devices are designed to enable a new class of geographically-distributed spectrum monitoring and analysis applications
31.
Heterostructure barrier varactor
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The heterostructure barrier varactor is a semiconductor device which shows a variable capacitance with voltage bias, similar to a varactor diode. Unlike a diode, it has an anti-symmetric current-voltage relationship and a symmetric capacitance-voltage relationship, the device was invented by Erik Kollberg together with Anders Rydberg in 1989 at Chalmers University of Technology. The inset of the shows the circuit schematic symbol of the HBV. From the symbol, one can conclude that the HBV consists of two, back to back, anti-serially connected rectifying diodes, the gap in the middle of the diode symbol represents the inherent capacitance of the device. The electrical characteristics of the HBV are realized by separating two layers of a material with a layer of another semiconductor material. The band-gap of material should be larger than for material and this results in a barrier for the carriers trying to travel through the layers --. The layers are usually n-doped which means that electrons are the majority carriers of this device, at different bias voltages the carriers are redistributed and the distance between the carriers on each side of the barrier is different. As a consequence the HBV has electrical properties resembling the parallel plate capacitor with a voltage dependent plate distance d, the main application for the HBV diode is to generate extremely high frequency signals from lower frequency input. This type of frequency multiplication is demonstrated as triplers at 100 GHz through 282 GHz and up to 450 GHz, the frequency multiplication is made possible by the highly nonlinear voltage dependence of the capacitance C. By feeding the HBV a signal of low frequency f1, higher harmonics f3=3f1, f5=5f1, only odd harmonics are generated, since even harmonics are cancelled due to the symmetric nature of the nonlinearity. Also, using this inherent symmetry of the device, it can operate without DC-biasing and this is an advantage compared to the Schottky diode which has to be biased. Signals generated at these frequencies have applications in areas such as radioastronomy, security imaging, biological and medical imaging
32.
Ferroelectric capacitor
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Ferroelectric capacitor is a capacitor based on a ferroelectric material. In contrast, traditional capacitors are based on dielectric materials, Ferroelectric devices are used in digital electronics as part of ferroelectric RAM, or in analog electronics as tunable capacitors. In memory applications, the value of a ferroelectric capacitor is read by applying an electric field. The amount of charge needed to flip the memory cell to the state is measured. This means that the read operation destroys the cell state. This makes it similar to the core memory. The requirement for a cycle for each read cycle, together with the high but not infinite write cycle limit. With perfect electrodes, λ =0 or for thick films, with d ≫ a the equation reduces to, V = E f d ⇒ E f = V d Ferroelectricity Ferroelectric RAM FeRAM Tutorial
33.
Adel Sedra
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Adel S. Sedra is an Egyptian Canadian electrical engineer and professor. Born in Egypt in 1943, Sedra received his B. Sc. from Cairo University in 1964 and his M. A. Sc. and Ph. D. from the University of Toronto, in 1968 and 1969, all three of his degrees are in electrical engineering. Sedra joined the faculty of the University of Toronto in 1969 and became professor in 1972. He served as chair of the Department of Electrical Engineering from 1986 to 1993, and was president, provost. In his nine years as provost Sedra led the university through two major long-range planning cycles in 1994 and 1998, on July 1,2003, Sedra joined the University of Waterloo as dean of its Faculty of Engineering and as professor of electrical and computer engineering. In 2004 he initiated the University of Waterloo Engineering Planning Exercise and he served as Dean of Engineering until June 2012. A specialist in microelectronics, Sedras research focuses on applications in communication and instrumentation systems, including theory, Sedra has co-authored three textbooks, including Microelectronic Circuits, now in its seventh edition. The text is published in ten languages, has one million copies in print. He is co-author with Gordon W. Roberts of the text book SPICE for Microelectronic Circuits published in 1995 and his first text book titled Filter Theory and Design, Active and Passive was published in 1978. Sedra has published about 150 scholarly papers, has guided the research of about 65 graduate students, and has served as a consultant to industry and governments in Canada. Sedra served as a delegate to Oxford University Press and is editing the Oxford Electrical. More recently, Sedra chaired a committee reviewed the Structure of NSERC Grant Selection Committees. For every year since 2003, it has awarded to a graduate student who demonstrates outstanding academic
34.
Oxford University Press
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Oxford University Press is the largest university press in the world, and the second oldest after Cambridge University Press. It is a department of the University of Oxford and is governed by a group of 15 academics appointed by the known as the delegates of the press. They are headed by the secretary to the delegates, who serves as OUPs chief executive, Oxford University has used a similar system to oversee OUP since the 17th century. The university became involved in the print trade around 1480, and grew into a printer of Bibles, prayer books. OUP took on the project became the Oxford English Dictionary in the late 19th century. Moves into international markets led to OUP opening its own offices outside the United Kingdom, by contracting out its printing and binding operations, the modern OUP publishes some 6,000 new titles around the world each year. OUP was first exempted from United States corporation tax in 1972, as a department of a charity, OUP is exempt from income tax and corporate tax in most countries, but may pay sales and other commercial taxes on its products. The OUP today transfers 30% of its surplus to the rest of the university. OUP is the largest university press in the world by the number of publications, publishing more than 6,000 new books every year, the Oxford University Press Museum is located on Great Clarendon Street, Oxford. Visits must be booked in advance and are led by a member of the archive staff, displays include a 19th-century printing press, the OUP buildings, and the printing and history of the Oxford Almanack, Alice in Wonderland and the Oxford English Dictionary. The first printer associated with Oxford University was Theoderic Rood, the first book printed in Oxford, in 1478, an edition of Rufinuss Expositio in symbolum apostolorum, was printed by another, anonymous, printer. Famously, this was mis-dated in Roman numerals as 1468, thus apparently pre-dating Caxton, roods printing included John Ankywylls Compendium totius grammaticae, which set new standards for teaching of Latin grammar. After Rood, printing connected with the university remained sporadic for over half a century, the chancellor, Robert Dudley, 1st Earl of Leicester, pleaded Oxfords case. Some royal assent was obtained, since the printer Joseph Barnes began work, Oxfords chancellor, Archbishop William Laud, consolidated the legal status of the universitys printing in the 1630s. Laud envisaged a unified press of world repute, Oxford would establish it on university property, govern its operations, employ its staff, determine its printed work, and benefit from its proceeds. To that end, he petitioned Charles I for rights that would enable Oxford to compete with the Stationers Company and the Kings Printer and these were brought together in Oxfords Great Charter in 1636, which gave the university the right to print all manner of books. Laud also obtained the privilege from the Crown of printing the King James or Authorized Version of Scripture at Oxford and this privilege created substantial returns in the next 250 years, although initially it was held in abeyance. The Stationers Company was deeply alarmed by the threat to its trade, under this, the Stationers paid an annual rent for the university not to exercise its full printing rights – money Oxford used to purchase new printing equipment for smaller purposes
35.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
36.
Integrated Authority File
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The Integrated Authority File or GND is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and increasingly also by archives, the GND is managed by the German National Library in cooperation with various regional library networks in German-speaking Europe and other partners. The GND falls under the Creative Commons Zero license, the GND specification provides a hierarchy of high-level entities and sub-classes, useful in library classification, and an approach to unambiguous identification of single elements. It also comprises an ontology intended for knowledge representation in the semantic web, available in the RDF format
37.
Electronic component
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An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components have a number of electrical terminals or leads and these leads connect to create an electronic circuit with a particular function. The following list of electronic components focuses on the version of these components. Components can be classified as passive, active, or electromechanic, the strict physics definition treats passive components as ones that cannot supply energy themselves, whereas a battery would be seen as an active component since it truly acts as a source of energy. However, electronic engineers who perform circuit analysis use a more restrictive definition of passivity, then, the analysis only concerns the AC circuit, an abstraction that ignores DC voltages and currents present in the real-life circuit. This fiction, for instance, lets us view an oscillator as producing energy even though in reality the oscillator consumes even more energy from a DC power supply, active components include amplifying components such as transistors, triode vacuum tubes, and tunnel diodes. Passive components cant introduce net energy into the circuit and they also cant rely on a source of power, except for what is available from the circuit they are connected to. As a consequence they cant amplify, although they may increase a voltage or current, passive components include two-terminal components such as resistors, capacitors, inductors, and transformers. In contrast, active components generally lack that property, conduct electricity easily in one direction, among more specific behaviors. A transistor is a device used to amplify and switch electronic signals. Resistors, capacitors, inductors, and transformers are all considered passive devices, pass current in proportion to voltage and oppose current. They are used for filtering power supply lines, tuning resonant circuits, transducers generate physical effects when driven by an electrical signal, or vice versa. Sensors are transducers that react to environmental conditions by changing their electrical properties or generating an electrical signal, the transducers listed here are single electronic components, and are passive. Only the most common ones are listed here, reference designators are applied to the symbols to identify the component
38.
Semiconductor device
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Semiconductor devices have replaced thermionic devices in most applications. They use electronic conduction in the state as opposed to the gaseous state or thermionic emission in a high vacuum. Semiconductor materials are useful because their behavior can be manipulated by the addition of impurities. Current conduction in a semiconductor occurs via mobile or free electrons and holes, doping a semiconductor such as silicon with a small amount of impurity atoms, such as phosphorus or boron, greatly increases the number of free electrons or holes within the semiconductor. The semiconductor material used in devices is doped under highly controlled conditions in a facility, or fab, to control precisely the location and concentration of p-. The junctions which form where n-type and p-type semiconductors join together are called p–n junctions, a semiconductor diode is a device typically made from a single p–n junction. At the junction of a p-type and an n-type semiconductor there forms a region where current conduction is inhibited by the lack of mobile charge carriers. Exposing a semiconductor to light can generate electron–hole pairs, which increases the number of free carriers, diodes optimized to take advantage of this phenomenon are known as photodiodes. Compound semiconductor diodes can also be used to light, as in light-emitting diodes. Bipolar junction transistors are formed from two p–n junctions, in either n–p–n or p–n–p configuration, the middle, or base, region between the junctions is typically very narrow. The other regions, and their terminals, are known as the emitter. A small current injected through the junction between the base and the changes the properties of the base-collector junction so that it can conduct current even though it is reverse biased. This creates a larger current between the collector and emitter, controlled by the base-emitter current. Another type of transistor, the transistor, operates on the principle that semiconductor conductivity can be increased or decreased by the presence of an electric field. An electric field can increase the number of electrons and holes in a semiconductor. The MOSFET, a device, is the most used semiconductor device today. The gate electrode is charged to produce a field that controls the conductivity of a channel between two terminals, called the source and drain. Depending on the type of carrier in the channel, the device may be an n-channel or a p-channel MOSFET, although the MOSFET is named in part for its metal gate, in modern devices polysilicon is typically used instead
39.
Avalanche diode
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In electronics, an avalanche diode is a diode that is designed to experience avalanche breakdown at a specified reverse bias voltage. The junction of a diode is designed to prevent current concentration and resulting hot spots. The avalanche breakdown is due to minority carriers accelerated enough to create ionization in the crystal lattice, because the avalanche breakdown is uniform across the whole junction, the breakdown voltage is nearly constant with changing current when compared to a non-avalanche diode. The Zener diode exhibits a similar effect in addition to Zener breakdown. Both effects are present in any such diode, but one usually dominates the other. This feature provides better protection than simple Zener diode and acts more like a gas discharge tube replacement. Avalanche diodes have a positive temperature coefficient of voltage, where diodes relying on the Zener effect have a negative temperature coefficient. The voltage after breakdown varies only slightly with changing current and this makes the avalanche diode useful as a type of voltage reference. Voltage reference diodes rated more than about 5.5 volts are generally avalanche diodes, Zener diodes are used to protect electronic circuits against damaging high voltages. The avalanche diode is connected to the circuit so that it is reverse-biased, in other words, its cathode is positive with respect to its anode. In this configuration, the diode is non-conducting and does not interfere with the circuit, if the voltage increases beyond the design limit, the diode goes into avalanche breakdown, causing the harmful voltage to be conducted to ground. When used in fashion, they are often referred to as clamping diodes or transient voltage suppressors because they fix or clamp the maximum voltage to a predetermined level. Avalanche diodes are normally specified for this role by their clamping voltage VBR, avalanche breakdown is not destructive as long as the diode is prevented from overheating. Avalanche diodes generate radio frequency noise and they are commonly used as noise sources in radio equipment and hardware random number generators. For instance, they are used as a source of RF for antenna analyzer bridges. Avalanche diodes can also be used as white noise generators, if placed into a resonant circuit, avalanche diodes can act as negative resistance devices. The IMPATT diode is an avalanche diode optimized for frequency generation and these are made from doped silicon and depend on the avalanche breakdown effect to detect even single photons. The silicon avalanche photodiode is a high gain photon detector and they are. ideal for use in high speed, low light level applications
40.
Transistor
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A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit, a voltage or current applied to one pair of the transistors terminals controls the current through another pair of terminals. Because the controlled power can be higher than the controlling power, today, some transistors are packaged individually, but many more are found embedded in integrated circuits. The transistor is the building block of modern electronic devices. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, the thermionic triode, a vacuum tube invented in 1907, enabled amplified radio technology and long-distance telephony. The triode, however, was a device that consumed a substantial amount of power. Physicist Julius Edgar Lilienfeld filed a patent for a transistor in Canada in 1925. Lilienfeld also filed patents in the United States in 1926 and 1928. However, Lilienfeld did not publish any research articles about his devices nor did his patents cite any examples of a working prototype. In 1934, German inventor Oskar Heil patented a device in Europe. Solid State Physics Group leader William Shockley saw the potential in this, the term transistor was coined by John R. Pierce as a contraction of the term transresistance. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first point-contact transistor, Mataré had previous experience in developing crystal rectifiers from silicon and germanium in the German radar effort during World War II. Using this knowledge, he began researching the phenomenon of interference in 1947, realizing that Bell Labs scientists had already invented the transistor before them, the company rushed to get its transistron into production for amplified use in Frances telephone network. The first bipolar junction transistors were invented by Bell labs William Shockley, on April 12,1950, Bell Labs chemists Gordon Teal and Morgan Sparks had successfully produced a working bipolar NPN junction amplifying germanium transistor. Bell Labs had made this new sandwich transistor discovery announcement, in a release on July 4,1951. The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953 and these were made by etching depressions into an N-type germanium base from both sides with jets of Indium sulfate until it was a few ten-thousandths of an inch thick
41.
Memristor
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A memristor is a hypothetical non-linear passive two-terminal electrical component relating electric charge and magnetic flux linkage. It was envisioned, and its name coined, in 1971 by circuit theorist Leon Chua. e and its present resistance depends on how much electric charge has flowed in what direction through it in the past, the device remembers its history — the so-called non-volatility property. When the electric supply is turned off, the memristor remembers its most recent resistance until it is turned on again. Following this claim, Leon Chua has argued that the definition could be generalized to cover all forms of two-terminal non-volatile memory devices based on resistance switching effects. There are, however, some doubts as to whether the memristor can actually exist in physical reality. Additionally, some experimental evidence contradicts Chuas generalization since a non-passive nanobattery effect is observable in resistance switching memory, Chua also argued that the memristor is the oldest known circuit element, with its effects predating the resistor, capacitor and inductor. These devices are intended for applications in nanoelectronic memories, computer logic, commercial availability of memristor memory has been estimated as 2018. In March 2012, a team of researchers from HRL Laboratories, in his 1971 paper, Chua extrapolated a conceptual symmetry between the nonlinear resistor, nonlinear capacitor and nonlinear inductor. He then inferred the possibility of a memristor as another fundamental nonlinear circuit element linking magnetic flux, in contrast to a linear resistor the memristor has a dynamic relationship between current and voltage including a memory of past voltages or currents. Other scientists had proposed dynamic memory resistors such as the memistor of Bernard Widrow, memristor resistance depends on the integral of the input applied to the terminals. Since the element remembers the amount of current that last passed through, another way of describing a memristor is as any passive two-terminal circuit element that maintains a functional relationship between the time integral of current and the time integral of voltage. The slope of this function is called the memristance M and is similar to variable resistance, the memristor definition is based solely on the fundamental circuit variables of current and voltage and their time-integrals, just like the resistor, capacitor and inductor. There is no such thing as a standard memristor, instead, each device implements a particular function, wherein the integral of voltage determines the integral of current, and vice versa. A linear time-invariant memristor, with a constant value for M, is simply a conventional resistor, manufactured devices are never purely memristors, but also exhibit some capacitance and resistance. According to the original 1971 definition, the memristor was the fundamental circuit element. In 2011 Chua argued for a definition that included all 2-terminal non-volatile memory devices based on resistance switching. Williams argued that MRAM, phase change memory and RRAM were memristor technologies, some researchers argued that biological structures such as blood and skin fit the definition. In 2011, Meuffels and Schroeder noted that one of the early memristor papers included a mistaken assumption regarding ionic conduction, in 2012, Meuffels and Soni discussed some fundamental issues and problems in the realization of memristors
42.
Bipolar junction transistor
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A bipolar junction transistor is a type of transistor that uses both electron and hole charge carriers. In contrast, unipolar transistors, such as transistors, only use one kind of charge carrier. For their operation, BJTs use two junctions between two types, n-type and p-type. BJTs are manufactured in two types, NPN and PNP, and are available as components, or fabricated in integrated circuits. The basic function of a BJT is to amplify current, by convention, the direction of current on diagrams is shown as the direction that a positive charge would move. However, current in many metal conductors is due to the flow of electrons which, because they carry a negative charge, on the other hand, inside a bipolar transistor, currents can be composed of both positively charged holes and negatively charged electrons. In this article, current arrows are shown in the conventional direction, the arrow on the symbol for bipolar transistors points in the direction conventional current travels. BJTs come in two types, or polarities, known as PNP and NPN based on the types of the three main terminal regions. An NPN transistor comprises two semiconductor junctions that share a thin p-doped region, and a PNP transistor comprises two semiconductor junctions that share a thin n-doped region, charge flow in a BJT is due to diffusion of charge carriers across a junction between two regions of different charge concentrations. The regions of a BJT are called emitter, collector, a discrete transistor has three leads for connection to these regions. Typically, the region is heavily doped compared to the other two layers, whereas the majority charge carrier concentrations in base and collector layers are about the same. This allows thermally excited electrons to inject from the emitter into the base region and these electrons diffuse through the base from the region of high concentration near the emitter towards the region of low concentration near the collector. The electrons in the base are called minority carriers because the base is doped p-type, in particular, the thickness of the base must be much less than the diffusion length of the electrons. The thin shared base and asymmetric collector–emitter doping are what differentiates a bipolar transistor from two separate and oppositely biased diodes connected in series, the collector–emitter current can be viewed as being controlled by the base–emitter current, or by the base–emitter voltage. These views are related by the relation of the base–emitter junction. The physical explanation for collector current is the concentration of minority carriers in the base region, due to low level injection the ambipolar transport rates is in effect determined by the excess minority carriers. Detailed transistor models of transistor action, such as the Gummel–Poon model, however, because base charge is not a signal that is visible at the terminals, the current- and voltage-control views are generally used in circuit design and analysis. In analog circuit design, the view is sometimes used because it is approximately linear
43.
Multigate device
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A multigate device or multiple-gate field-effect transistor refers to a MOSFET that incorporates more than one gate into a single device. The multiple gates may be controlled by a gate electrode, wherein the multiple gate surfaces act electrically as a single gate. A multigate device employing independent gate electrodes is called a multiple-independent-gate field-effect transistor. The primary roadblock to widespread implementation is manufacturability, as both planar and non-planar designs present significant challenges, especially with respect to lithography and patterning, other complementary strategies for device scaling include channel strain engineering, silicon-on-insulator-based technologies, and high-k/metal gate materials. Dual-gate MOSFETs are commonly used in VHF mixers and in sensitive VHF front-end amplifiers and they are available from manufacturers such as Motorola, NXP, and Hitachi. Dozens of multigate transistor variants may be found in the literature, in general, these variants may be differentiated and classified in terms of architecture and number of channels/gates. The first international demonstration of the devices family using thin Silicon film was performed with a double-gate MOSFET. The double-gate control of silicon-on-insulator transistors was used to force the whole film in strong inversion or strong accumulation. A simulation program and experiments on SIMOX structures was used to study this new type of device, in planar double-gate transistors the drain–source channel is sandwiched between two independently fabricated gate/gate-oxide stacks. The primary challenge in fabricating such structures is achieving satisfactory self-alignment between the upper and lower gates, flexFET is a planar, independently double-gated transistor with a damascene metal top gate MOSFET and an implanted JFET bottom gate that are self-aligned in a gate trench. This device is highly due to its sub-lithographic channel length, non-implanted ultra-shallow source and drain extensions, non-epi raised source and drain regions. Flexfet was developed and is manufactured by American Semiconductor, Inc, the term FinFET was coined by University of California, Berkeley, researchers to describe a nonplanar, double-gate transistor built on an SOI substrate, based on the earlier DELTA transistor design. The distinguishing characteristic of the FinFET is that the channel is wrapped by a thin silicon fin. The thickness of the fin determines the channel length of the device. The wrap-around gate structure provides an electrical control over the channel and thus helps in reducing the leakage current. In current usage the term FinFET has a precise definition. In the technical literature, FinFET is used generically to describe any fin-based. A25 nm transistor operating on just 0.7 volt was demonstrated in December 2002 by TSMC, the Omega FinFET design is named after the similarity between the Greek letter omega and the shape in which the gate wraps around the source/drain structure
