A microprocessor is a computer processor that incorporates the functions of a central processing unit on a single integrated circuit, or at most a few integrated circuits. The microprocessor is a multipurpose, clock driven, register based, digital integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, provides results as output. Microprocessors contain sequential digital logic. Microprocessors operate on symbols represented in the binary number system; the integration of a whole CPU onto a single or a few integrated circuits reduced the cost of processing power. Integrated circuit processors are produced in large numbers by automated processes, resulting in a low unit price. Single-chip processors increase reliability because there are many fewer electrical connections that could fail; as microprocessor designs improve, the cost of manufacturing a chip stays the same according to Rock's law. Before microprocessors, small computers had been built using racks of circuit boards with many medium- and small-scale integrated circuits.
Microprocessors combined this into a few large-scale ICs. Continued increases in microprocessor capacity have since rendered other forms of computers completely obsolete, with one or more microprocessors used in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers; the complexity of an integrated circuit is bounded by physical limitations on the number of transistors that can be put onto one chip, the number of package terminations that can connect the processor to other parts of the system, the number of interconnections it is possible to make on the chip, the heat that the chip can dissipate. Advancing technology makes more powerful chips feasible to manufacture. A minimal hypothetical microprocessor might include only an arithmetic logic unit, a control logic section; the ALU performs addition and operations such as AND or OR. Each operation of the ALU sets one or more flags in a status register, which indicate the results of the last operation.
The control logic retrieves instruction codes from memory and initiates the sequence of operations required for the ALU to carry out the instruction. A single operation code might affect many individual data paths and other elements of the processor; as integrated circuit technology advanced, it was feasible to manufacture more and more complex processors on a single chip. The size of data objects became larger. Additional features were added to the processor architecture. Floating-point arithmetic, for example, was not available on 8-bit microprocessors, but had to be carried out in software. Integration of the floating point unit first as a separate integrated circuit and as part of the same microprocessor chip sped up floating point calculations. Physical limitations of integrated circuits made such practices as a bit slice approach necessary. Instead of processing all of a long word on one integrated circuit, multiple circuits in parallel processed subsets of each data word. While this required extra logic to handle, for example and overflow within each slice, the result was a system that could handle, for example, 32-bit words using integrated circuits with a capacity for only four bits each.
The ability to put large numbers of transistors on one chip makes it feasible to integrate memory on the same die as the processor. This CPU cache has the advantage of faster access than off-chip memory and increases the processing speed of the system for many applications. Processor clock frequency has increased more than external memory speed, so cache memory is necessary if the processor is not delayed by slower external memory. A microprocessor is a general-purpose entity. Several specialized processing devices have followed: A digital signal processor is specialized for signal processing. Graphics processing units are processors designed for realtime rendering of images. Other specialized units exist for video machine vision. Microcontrollers integrate a microprocessor with peripheral devices in embedded systems. Systems on chip integrate one or more microprocessor or microcontroller cores. Microprocessors can be selected for differing applications based on their word size, a measure of their complexity.
Longer word sizes allow each clock cycle of a processor to carry out more computation, but correspond to physically larger integrated circuit dies with higher standby and operating power consumption. 4, 8 or 12 bit processors are integrated into microcontrollers operating embedded systems. Where a system is expected to handle larger volumes of data or require a more flexible user interface, 16, 32 or 64 bit processors are used. An 8- or 16-bit processor may be selected over a 32-bit processor for system on a chip or microcontroller applications that require low-power electronics, or are part of a mixed-signal integrated circuit with noise-sensitive on-chip analog electronics such as high-resolution analog to digital converters, or both. Running 32-bit arithmetic on an 8-bit chip could end up using more power, as the chip must execute software with multiple instructions. Thousands of items that were traditionally not computer-related inc
Lynn Ann Conway is an American computer scientist, electrical engineer and transgender activist. Conway is notable for a number of pioneering achievements, including the Mead & Conway revolution in VLSI design, which incubated an emerging electronic design automation industry, she worked at IBM in the 1960s and is credited with the invention of generalized dynamic instruction handling, a key advance used in out-of-order execution, used by most modern computer processors to improve performance. Conway grew up in New York. Conway was experienced gender dysphoria as a child, she did well in math and science in high school. Conway entered MIT in 1955, earning high grades but leaving in despair after an attempted gender transition in 1957–58 failed due to the medical climate at the time. After working as an electronics technician for several years, Conway resumed education at Columbia University's School of Engineering and Applied Science, earning B. S. and M. S. E. E. Degrees in 1962 and 1963. Conway was recruited by IBM Research in Yorktown Heights, New York in 1964, was soon selected to join the architecture team designing an advanced supercomputer, working alongside John Cocke, Herbert Schorr, Ed Sussenguth, Fran Allen and other IBM researchers on the Advanced Computing Systems project, inventing multiple-issue out-of-order dynamic instruction scheduling while working there.
The Computer History Museum has stated that "the ACS machines appears to have been the first superscalar design, a computer architectural paradigm exploited in modern high-performance microprocessors." After learning of the pioneering research of Harry Benjamin in treating transsexuals and realising that genital affirmation surgery was now possible, Conway sought his help and became his patient. After suffering from severe depression from gender dysphoria, Conway contacted Benjamin, who agreed to providing counseling and prescribe hormones. Under Benjamin's care, Conway began her gender transition. While struggling with life in a male role, Conway had two children. Under the legal constraints in place, after transitioning she was denied access to their children. Although she had hoped to be allowed to transition on the job, IBM fired Conway in 1968 after she revealed her intention to transition to a female gender role. Upon completing her transition in 1968, Conway took a new name and identity, restarted her career in what she called "stealth-mode" as a contract programmer at Computer Applications, Inc.
She went on to work at Memorex during 1969 -- 1972 as a digital system computer architect. Conway joined Xerox PARC in 1973. Collaborating with Carver Mead of Caltech on VLSI design methodology, she co-authored Introduction to VLSI Systems, a groundbreaking work that would soon become a standard textbook in chip design, used in over 100 universities by 1983; the book and early courses were the beginning of the Conway revolution in VLSI system design. In 1978, Conway served as visiting associate professor of EECS at MIT, teaching a now famous VLSI design course based on a draft of the Mead–Conway text; the course validated the new design methods and textbook, established the syllabus and instructor's guidebook used in courses all around the world. Among Conway's contributions were invention of dimensionless, scalable design rules that simplified chip design and design tools, invention of a new form of internet-based infrastructure for rapid-prototyping and short-run fabrication of large numbers of chip designs.
The new infrastructure was institutionalized as the MOSIS system in 1981. Since MOSIS has fabricated more than 50,000 circuit designs for commercial firms, government agencies, research and educational institutions around the world. Prominent VLSI researcher Charles Seitz commented that "MOSIS represented the first period since the pioneering work of Eckert and Mauchley on the ENIAC in the late 1940s that universities and small companies had access to state-of-the-art digital technology."The research methods used to develop the Mead–Conway VLSI design methodology and the MOSIS prototype are documented in a 1981 Xerox report and the Euromicro Journal. The impact of the Mead–Conway work is described and time-lined in a number of historical overviews of computing. Conway and her colleagues have compiled an online archive of original papers that documents much of that work. In the early 1980s, Conway left Xerox to join DARPA, where she was a key architect of the Defense Department's Strategic Computing Initiative, a research program studying high-performance computing, autonomous systems technology, intelligent weapons technology.
In a USA Today article about Conway's joining DARPA, Mark Stefik, a Xerox scientist who worked with her, said "Lynn would like to live five lives in the course of one life" and that she's "charismatic and energetic". Douglas Fairbairn, a former Xerox associate, said "She figures out a way so that everybody wins."As sociologist Thomas Streeter discusses in The Net Effect: "By taking this job, Conway was demonstrating that she was no antiwar liberal.". But Conway carried a sense of computers as tools for horizontal communications that she had absorbed at PARC right into DARPA - at one of the hottest moments of the cold war." Conway joined the University of Michigan in 1985 as professor of electrical engineering and computer science, associate dean of engineering
An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, silicon. The integration of large numbers of tiny transistors into a small chip results in circuits that are orders of magnitude smaller and faster than those constructed of discrete electronic components; the IC's mass production capability and building-block approach to circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs. Integrated circuits were made practical by mid-20th-century technology advancements in semiconductor device fabrication. Since their origins in the 1960s, the size and capacity of chips have progressed enormously, driven by technical advances that fit more and more transistors on chips of the same size – a modern chip may have many billions of transistors in an area the size of a human fingernail.
These advances following Moore's law, make computer chips of today possess millions of times the capacity and thousands of times the speed of the computer chips of the early 1970s. ICs have two main advantages over discrete circuits: performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the IC's components switch and consume comparatively little power because of their small size and close proximity; the main disadvantage of ICs is the high cost to fabricate the required photomasks. This high initial cost means. An integrated circuit is defined as: A circuit in which all or some of the circuit elements are inseparably associated and electrically interconnected so that it is considered to be indivisible for the purposes of construction and commerce. Circuits meeting this definition can be constructed using many different technologies, including thin-film transistors, thick-film technologies, or hybrid integrated circuits.
However, in general usage integrated circuit has come to refer to the single-piece circuit construction known as a monolithic integrated circuit. Arguably, the first examples of integrated circuits would include the Loewe 3NF. Although far from a monolithic construction, it meets the definition given above. Early developments of the integrated circuit go back to 1949, when German engineer Werner Jacobi filed a patent for an integrated-circuit-like semiconductor amplifying device showing five transistors on a common substrate in a 3-stage amplifier arrangement. Jacobi disclosed cheap hearing aids as typical industrial applications of his patent. An immediate commercial use of his patent has not been reported; the idea of the integrated circuit was conceived by Geoffrey Dummer, a radar scientist working for the Royal Radar Establishment of the British Ministry of Defence. Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington, D. C. on 7 May 1952.
He gave many symposia publicly to propagate his ideas and unsuccessfully attempted to build such a circuit in 1956. A precursor idea to the IC was to create small ceramic squares, each containing a single miniaturized component. Components could be integrated and wired into a bidimensional or tridimensional compact grid; this idea, which seemed promising in 1957, was proposed to the US Army by Jack Kilby and led to the short-lived Micromodule Program. However, as the project was gaining momentum, Kilby came up with a new, revolutionary design: the IC. Newly employed by Texas Instruments, Kilby recorded his initial ideas concerning the integrated circuit in July 1958 demonstrating the first working integrated example on 12 September 1958. In his patent application of 6 February 1959, Kilby described his new device as "a body of semiconductor material … wherein all the components of the electronic circuit are integrated." The first customer for the new invention was the US Air Force. Kilby won the 2000 Nobel Prize in Physics for his part in the invention of the integrated circuit.
His work was named an IEEE Milestone in 2009. Half a year after Kilby, Robert Noyce at Fairchild Semiconductor developed a new variety of integrated circuit, more practical than Kilby's implementation. Noyce's design was made of silicon. Noyce credited Kurt Lehovec of Sprague Electric for the principle of p–n junction isolation, a key concept behind the IC; this isolation allows each transistor to operate independently despite being part of the same piece of silicon. Fairchild Semiconductor was home of the first silicon-gate IC technology with self-aligned gates, the basis of all modern CMOS integrated circuits; the technology was developed by Italian physicist Federico Faggin in 1968. In 1970, he joined Intel in order to develop the first single-chip central processing unit microprocessor, the Intel 4004, for which he received the National Medal of Technology and Innovation in 2010; the 4004 was designed by Busicom's Masatoshi Shima and Intel's Ted Hoff in 1969, but it was Faggin's improved design in 1970 that made it a reality.
Advances in IC technology smaller features and la
Photolithography called optical lithography or UV lithography, is a process used in microfabrication to pattern parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a photosensitive chemical photoresist on the substrate. A series of chemical treatments either etches the exposure pattern into the material or enables deposition of a new material in the desired pattern upon the material underneath the photoresist. In complex integrated circuits, a CMOS wafer may go through the photolithographic cycle as many as 50 times. Photolithography shares some fundamental principles with photography in that the pattern in the photresist etching is created by exposing it to light, either directly or with a projected image using a photomask; this procedure is comparable to a high precision version of the method used to make printed circuit boards. Subsequent stages in the process have more in common with etching than with lithographic printing; this method can create small patterns, down to a few tens of nanometers in size.
It provides precise control of the shape and size of the objects it creates and can create patterns over an entire surface cost-effectively. Its main disadvantages are that it requires a flat substrate to start with, it is not effective at creating shapes that are not flat, it can require clean operating conditions. Photolithography is the standard method of printed circuit microprocessor fabrication; the root words photo and graphy all have Greek origins, with the meanings'light','stone' and'writing' respectively. As suggested by the name compounded from them, photolithography is a printing method in which light plays an essential role. In the 1820s, Nicephore Niepce invented a photographic process that used Bitumen of Judea, a natural asphalt, as the first photoresist. A thin coating of the bitumen on a sheet of metal, glass or stone became less soluble where it was exposed to light; the light-sensitivity of bitumen was poor and long exposures were required, but despite the introduction of more sensitive alternatives, its low cost and superb resistance to strong acids prolonged its commercial life into the early 20th century.
In 1940, Oskar Süß created a positive photoresist by using diazonaphthoquinone, which worked in the opposite manner: the coating was insoluble and was rendered soluble where it was exposed to light. In 1954, Louis Plambeck Jr. developed the Dycryl polymeric letterpress plate, which made the platemaking process faster. In 1952, the U. S. military assigned Jay W. Lathrop and James R. Nall at the National Bureau of Standards with the task of finding a way to reduce the size of electronic circuits in order to better fit the necessary circuitry in the limited space available inside a proximity fuze. Inspired by the application of photoresist, a photosensitive liquid used to mark the boundaries of rivet holes in metal aircraft wings, Nall determined that a similar process can be used to protect the germanium in the transistors and pattern the surface with light. During development and Nall were successful in creating a 2D miniaturized hybrid integrated circuit with transistors using this technique.
In 1958, during the IRE Professional Group on Electron Devices conference in Washington, D. C. they presented the first paper to describe the fabrication of transistors using photographic techniques and adopted the term “photolithography” to describe the process, marking the first published use of the term to describe semiconductor device patterning. Despite the fact that photolithography of electronic components concerns etching metal duplicates, rather than etching stone to produce a "master" as in conventional lithographic printing and Nall chose the term “photolithography” over “photoetching” because the former sounded “high tech.” A year after the conference and Nall’s patent on photolithography was formally approved on June 9, 1959. Photolithography would contribute to the development of the first semiconductor ICs as well as the first microchips. A single iteration of photolithography combines several steps in sequence. Modern cleanrooms use robotic wafer track systems to coordinate the process.
The procedure described here omits some advanced treatments, such as thinning agents or edge-bead removal. If organic or inorganic contaminations are present on the wafer surface, they are removed by wet chemical treatment, e.g. the RCA clean procedure based on solutions containing hydrogen peroxide. Other solutions made with trichloroethylene, acetone or methanol can be used to clean; the wafer is heated to a temperature sufficient to drive off any moisture that may be present on the wafer surface, 150 °C for ten minutes is sufficient. Wafers that have been in storage must be chemically cleaned to remove contamination. A liquid or gaseous "adhesion promoter", such as Bisamine, is applied to promote adhesion of the photoresist to the wafer; the surface layer of silicon dioxide on the wafer reacts with HMDS to form tri-methylated silicon-dioxide, a water repellent layer not unlike the layer of wax on a car's paint. This water repellent layer prevents the aqueous developer from penetrating between the photoresist layer and the wafer's
A semiconductor material has an electrical conductivity value falling between that of a metal, like copper, etc. and an insulator, such as glass. Their resistance decreases as their temperature increases, behaviour opposite to that of a metal, their conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created; the behavior of charge carriers which include electrons and electron holes at these junctions is the basis of diodes and all modern electronics. Some examples of semiconductors are silicon and gallium arsenide. After silicon, gallium arsenide is the second most common semiconductor used in laser diodes, solar cells, microwave frequency integrated circuits, others. Silicon is a critical element for fabricating most electronic circuits. Semiconductor devices can display a range of useful properties such as passing current more in one direction than the other, showing variable resistance, sensitivity to light or heat.
Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification and energy conversion. The conductivity of silicon is increased by adding a small amount of trivalent atoms; this process is known as doping and resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature; this is contrary to the behaviour of a metal in which conductivity decreases with increase in temperature. The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping increases the number of charge carriers within the crystal; when a doped semiconductor contains free holes it is called "p-type", when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants.
A single semiconductor crystal can have many p- and n-type regions. Although some pure elements and many compounds display semiconductor properties, silicon and compounds of gallium are the most used in electronic devices. Elements near the so-called "metalloid staircase", where the metalloids are located on the periodic table, are used as semiconductors; some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics in turn allowed the development of the transistor in 1947 and the integrated circuit in 1958. Variable electrical conductivity Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, semiconductors have their valence bands filled, preventing the entry flow of new electrons.
There are several developed techniques that allow semiconducting materials to behave like conducting materials, such as doping or gating. These modifications have two outcomes: p-type; these refer to the shortage of electrons, respectively. An unbalanced number of electrons would cause a current to flow through the material. Heterojunctions Heterojunctions occur when two differently doped semiconducting materials are joined together. For example, a configuration could consist of n-doped germanium; this results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, the p-doped germanium would have an excess of holes; the transfer occurs until equilibrium is reached by a process called recombination, which causes the migrating electrons from the n-type to come in contact with the migrating holes from the p-type. A product of this process is charged ions. Excited electrons A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation.
This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion. Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes; such disruptions can occur as a result of a temperature difference or photons, which can enter the system and create electrons and holes. The process that creates and annihilates electrons and holes are called generation and recombination. Light emission In certain semiconductors, excited electrons can relax by emitting light instead of producing heat; these semiconductors are used in the construction of light-emitting diodes and fluorescent quantum dots. High thermal conductivitySemiconductors with high thermal conductivity can be used for heat dissipation and improving thermal management of electronics. Thermal energy conversion Semiconductors have large thermoelectric power factors making them useful in thermoelectric generators, as well as high thermoelectric figures of merit making them useful in thermoelectric coolers.
A large number of elements and compounds have semiconducting properties, including: Certain pure elements are found in Group 14 of the p
A diode is a two-terminal electronic component that conducts current in one direction. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. Semiconductor diodes were the first semiconductor electronic devices; the discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other materials such as gallium arsenide and germanium are used; the most common function of a diode is to allow an electric current to pass in one direction, while blocking it in the opposite direction. As such, the diode can be viewed as an electronic version of a check valve; this unidirectional behavior is called rectification, is used to convert alternating current to direct current.
Forms of rectifiers, diodes can be used for such tasks as extracting modulation from radio signals in radio receivers. However, diodes can have more complicated behavior than this simple on–off action, because of their nonlinear current-voltage characteristics. Semiconductor diodes begin conducting electricity only if a certain 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, is a function of temperature. Diodes' high resistance to current flowing in the reverse direction drops to a low resistance when the reverse voltage across the diode reaches a value called the breakdown voltage. A semiconductor diode's 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. For example, diodes are used to regulate voltage, to protect circuits from high voltage surges, to electronically tune radio and TV receivers, to generate radio-frequency oscillations, to produce light.
Tunnel, Gunn and IMPATT diodes exhibit negative resistance, useful in microwave and switching circuits. Diodes, both vacuum and semiconductor, can be used as shot-noise generators. Thermionic diodes and solid-state diodes were developed separately, at the same time, in the early 1900s, as radio receiver detectors; until the 1950s, vacuum diodes were used more in radios because the early point-contact semiconductor diodes were less stable. In addition, most receiving sets had vacuum tubes for amplification that could have the thermionic diodes included in the tube, vacuum-tube rectifiers and gas-filled rectifiers were capable of handling some high-voltage/high-current rectification tasks better than the semiconductor diodes that were available at that time. In 1873, Frederick Guthrie observed that a grounded, white hot metal ball brought in close proximity to an electroscope would discharge a positively charged electroscope, but not a negatively charged electroscope. In 1880, Thomas Edison observed unidirectional current between heated and unheated elements in a bulb called Edison effect, was granted a patent on application of the phenomenon for use in a dc voltmeter.
About 20 years John Ambrose Fleming realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on November 16, 1904. Throughout the vacuum tube era, valve diodes were used in all electronics such as radios, sound systems and instrumentation, they lost market share beginning in the late 1940s due to selenium rectifier technology and to semiconductor diodes during the 1960s. Today they are still used in a few high power applications where their ability to withstand transient voltages and their robustness gives them an advantage over semiconductor devices, in musical instrument and audiophile applications. In 1874, German scientist Karl Ferdinand Braun discovered the "unilateral conduction" across a contact between a metal and a mineral. Indian scientist Jagadish Chandra Bose was the first to use a crystal for detecting radio waves in 1894; the crystal detector was developed into a practical device for wireless telegraphy by Greenleaf Whittier Pickard, who invented a silicon crystal detector in 1903 and received a patent for it on November 20, 1906.
Other experimenters tried a variety of other minerals as detectors. Semiconductor principles were unknown to the developers of these early rectifiers. During the 1930s understanding of physics advanced and in the mid 1930s researchers at Bell Telephone Laboratories recognized the potential of the crystal detector for application in microwave technology. Researchers at Bell Labs, Western Electric, MIT, Purdue and in the UK intensively developed point-contact diodes during World War II for application in ra
A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals; because the controlled power can be higher than the controlling power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits; the transistor is the fundamental building block of modern electronic devices, is ubiquitous in modern electronic systems. 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 implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, William Shockley. The transistor revolutionized the field of electronics, paved the way for smaller and cheaper radios and computers, among other things.
The transistor is on the list of IEEE milestones in electronics, Bardeen and Shockley shared the 1956 Nobel Prize in Physics for their achievement. Most transistors are made from pure silicon or germanium, but certain other semiconductor materials can be used. A transistor may have only one kind of charge carrier, in a field effect transistor, or may have two kinds of charge carriers in bipolar junction transistor devices. Compared with the vacuum tube, transistors are smaller, require less power to operate. Certain vacuum tubes have advantages over transistors at high operating frequencies or high operating voltages. Many types of transistors are made to standardized specifications by multiple manufacturers; the thermionic triode, a vacuum tube invented in 1907, enabled amplified radio technology and long-distance telephony. The triode, was a fragile device that consumed a substantial amount of power. In 1909 physicist William Eccles discovered the crystal diode oscillator. Physicist Julius Edgar Lilienfeld filed a patent for a field-effect transistor in Canada in 1925, intended to be a solid-state replacement for the triode.
Lilienfeld filed identical 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 specific examples of a working prototype; because the production of high-quality semiconductor materials was still decades away, Lilienfeld's solid-state amplifier ideas would not have found practical use in the 1920s and 1930s if such a device had been built. In 1934, German inventor Oskar Heil patented a similar device in Europe. From November 17, 1947, to December 23, 1947, John Bardeen and Walter Brattain at AT&T's Bell Labs in Murray Hill, New Jersey of the United States performed experiments and observed that when two gold point contacts were applied to a crystal of germanium, a signal was produced with the output power greater than the input. Solid State Physics Group leader William Shockley saw the potential in this, over the next few months worked to expand the knowledge of semiconductors; the term transistor was coined by John R. Pierce as a contraction of the term transresistance.
According to Lillian Hoddeson and Vicki Daitch, authors of a biography of John Bardeen, Shockley had proposed that Bell Labs' first patent for a transistor should be based on the field-effect and that he be named as the inventor. Having unearthed Lilienfeld’s patents that went into obscurity years earlier, lawyers at Bell Labs advised against Shockley's proposal because the idea of a field-effect transistor that used an electric field as a "grid" was not new. Instead, what Bardeen and Shockley invented in 1947 was the first point-contact transistor. In acknowledgement of this accomplishment, Shockley and Brattain were jointly awarded the 1956 Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect". In 1948, the point-contact transistor was independently invented by German physicists Herbert Mataré and Heinrich Welker while working at the Compagnie des Freins et Signaux, a Westinghouse subsidiary located in Paris. 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. By June 1948, witnessing currents flowing through point-contacts, Mataré produced consistent results using samples of germanium produced by Welker, similar to what Bardeen and Brattain had accomplished earlier in December 1947. Realizing that Bell Labs' scientists had invented the transistor before them, the company rushed to get its "transistron" into production for amplified use in France's telephone network; the first bipolar junction transistors were invented by Bell Labs' William Shockley, which applied for patent on June 26, 1948. On April 12, 1950, Bell Labs chemists Gordon Teal and Morgan Sparks had produced a working bipolar NPN junction amplifying germanium transistor. Bell Labs had announced the discovery of this new "sandwich" transistor in a press release on July 4, 1951; the first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating up to 60 MHz.
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. Indium electroplated into the depressions formed the emitter; the first "prototype" pocket transistor radio was shown by I