Electronic oscillator

An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal a sine wave or a square wave. Oscillators convert direct current from a power supply to an alternating current signal, they are used in many electronic devices ranging from simplest clock generators to digital instruments and complex computers and peripherals etc. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, the sounds produced by electronic beepers and video games. Oscillators are characterized by the frequency of their output signal: A low-frequency oscillator is an electronic oscillator that generates a frequency below 20 Hz; this term is used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator. An audio oscillator produces frequencies in about 16 Hz to 20 kHz. An RF oscillator produces signals in the radio frequency range of about 100 kHz to 100 GHz.

Oscillators designed to produce a high-power AC output from a DC supply are called inverters. There are two main types of electronic oscillator – the linear or harmonic oscillator and the nonlinear or relaxation oscillator. Crystal oscillators are ubiquitous in modern electronics and produce frequencies from 32 kHz to over 150 MHz, with 32 kHz crystals commonplace in time keeping and the higher frequencies commonplace in clock generation and RF applications; the harmonic, or linear, oscillator produces a sinusoidal output. There are two types: The most common form of linear oscillator is an electronic amplifier such as a transistor or operational amplifier connected in a feedback loop with its output fed back into its input through a frequency selective electronic filter to provide positive feedback; when the power supply to the amplifier is first switched on, electronic noise in the circuit provides a non-zero signal to get oscillations started. The noise travels around the loop and is amplified and filtered until quickly it converges on a sine wave at a single frequency.

Feedback oscillator circuits can be classified according to the type of frequency selective filter they use in the feedback loop: In an RC oscillator circuit, the filter is a network of resistors and capacitors. RC oscillators are used to generate lower frequencies, for example in the audio range. Common types of RC oscillator circuits are the phase shift oscillator and the Wien bridge oscillator. In an LC oscillator circuit, the filter is a tuned circuit consisting of an inductor and capacitor connected together. Charge flows back and forth between the capacitor's plates through the inductor, so the tuned circuit can store electrical energy oscillating at its resonant frequency. There are small losses in the tank circuit, but the amplifier compensates for those losses and supplies the power for the output signal. LC oscillators are used at radio frequencies, when a tunable frequency source is necessary, such as in signal generators, tunable radio transmitters and the local oscillators in radio receivers.

Typical LC oscillator circuits are the Hartley and Clapp circuits. In a crystal oscillator circuit the filter is a piezoelectric crystal; the crystal mechanically vibrates as a resonator, its frequency of vibration determines the oscillation frequency. Crystals have a high Q-factor and better temperature stability than tuned circuits, so crystal oscillators have much better frequency stability than LC or RC oscillators. Crystal oscillators are the most common type of linear oscillator, used to stabilize the frequency of most radio transmitters, to generate the clock signal in computers and quartz clocks. Crystal oscillators use the same circuits as LC oscillators, with the crystal replacing the tuned circuit. Quartz crystals are limited to frequencies of 30 MHz or below. Other types of resonators, dielectric resonators and surface acoustic wave devices, are used to control higher frequency oscillators, up into the microwave range. For example, SAW oscillators are used to generate the radio signal in cell phones.

In addition to the feedback oscillators described above, which use two-port amplifying active elements such as transistors and operational amplifiers, linear oscillators can be built using one-port devices with negative resistance, such as magnetron tubes, tunnel diodes, IMPATT diodes and Gunn diodes. Negative-resistance oscillators are used at high frequencies in the microwave range and above, since at these frequencies feedback oscillators perform poorly due to excessive phase shift in the feedback path. In negative-resistance oscillators, a resonant circuit, such as an LC circuit, crystal, or cavity resonator, is connected across a device with negative differential resistance, a DC bias voltage is applied to supply energy. A resonant circuit by itself is "almost" an oscillator; the negative resistance of the active device cancels the internal loss resistance in the resonator, in effect creating a resonator with no damping, which generates spontaneous continuous oscillations at its resonant frequency.

The negative-resistance oscillator model is not limited to one-port devices like diodes. At high frequencies, transis


The Snoid referred to as Mr. Snoid, is an American underground comix character created by Robert Crumb in the mid-1960s. A diminutive sex fiend and irritating presence, the Snoid appears with other Crumb characters Angelfood McSpade, Mr. Natural, Crumb's own self-caricature. Crumb created the Snoid in his sketchbook in the winter of 1965/1966. After more strips published in underground papers the East Village Other and the Chicago Seed, the Snoid's first true comics appearance was in Snatch Comics #2, from 1969 until 1973 he appeared in many Crumb comics, including Zap Comix, Motor City Comics, Home Grown Funnies, Your Hytone Comics, Big Ass Comics, Mr. Natural, Black and White Comics; the character was satirized by cartoonist Daniel Clyne as "Doctor Frigmund Snoid" in Bijou Funnies #4, in the story "Dr. Lum Bago"; the character appeared in his own title in Snoid Comics, which featured six new stories. Many of the Snoid's adventures were collected in April 1998 in The Complete Crumb Comics #13 - "The Season of the Snoid," published by Fantagraphics.

His stories have been translated into German, French and Swedish. According to an early strip, the Snoid is from Wisconsin. Other stories portray multiple Snoids in existence. In one story, a "certain mountain" in Tibet is filled with numerous Snoids who sexually assault "Horny Harriet Hotpants". Another story portrays Mr. Snoid living inside a woman's rectum, but ends with a plea to help the other Snoids "walking the streets and lonely."In a story that appeared in Mr. Natural #2, Mr. Snoid has inspired a cult called The Snoidians, who cart him around on the shoulders of the "Giant Daughter of the Snoidvoid." The Snoidians battle with the "Mr. Naturalists," destroying the Snoid's conveyance and forcing him and Mr. Natural to escape the violence together. Underground comix authority M. Steven Fox wrote about the Snoid... The... character is, bottom line, a short-statured asshole, many people believe that Snoid, with his fetishes, sex cravings and disdain for materialism, is little more than an alter ego for Crumb.

One of those people is Crumb's own brother Maxon, who wrote about the Snoid's purpose in The Complete Crumb #13, "It was like with Carl Barks and his character Scrooge McDuck: Robert and the Snoid. With Barks it was money, with Robert. "Hey Boparee Bop," Yarrowstalks #2 — with Gar, Jesus Christ, Mr. Natural, Angelfood McSpade "The Old Pooperoo Pauses to Ponder / I Wanna Go Home! / You're Gonna Get There Anyway!", in East Village Other vol. 3, #2 — with The Old Pooperoo, Flakey Foont, Mr. Natural, Speed Freak, Angelfood McSpade "All Asshole Comics," Chicago Seed vol. 3 #1 — with Angelfood McSpade "Zap Comics Tells It Like It Is!!" (promo, Zap Comix #2 — with Biceps Bunny "Everyday Funnies with'The Snoid from Sheboygan'," East Village Other vol. 3, #43 untitled, East Village Other vol. 3, #47 — with Mr. Natural "Look Out Girls!! The Grabbies are Coming!!", Snatch Comics #2 Zap Comix #0 "Freak Out Funnies" — co-starring Spacemen untitled — with Angelfood McSpade untitled, Jiz Comics "Night of Terror," Motor City Comics #2 — with Shuman the Human "Backwater Blues,"' Home Grown Funnies #1 — with Angelfood McDevilsfood Your Hytone Comics "Horny Harriet Hotpants" — with Horny Harriet Hotpants, Orra Lee, Recta Lee, Jesus "Pete the Plumber" — intro only Big Ass Comics #2 "Anal Antics" — with the Landlady "And Now, A Word to You Feminist Women" — cameo alongside Robert Crumb untitled, Mr. Natural #2 — with Mr. Natural "The Nightmare," Promethean Enterprises #4 Black and White Comics untitled — with Will Shade, Ishman Bracey, Crazy Ed, Erton Snoody, Bill the Pill "Big Fine Legs" "Once I Led the Life of a Millionaire," Carload o' Comics — with Mr. Natural Snoid Comics "Mr. Snoid: Meet the Snoid" "This Cartooning is Tricky Business!" — with Robert Crumb "The Snoid Goes Bohemian" — with Beverly Baumstein "How Snoids are Born" "One Foot to Heaven" — with Sweet "Mr. Snoid Among His Fellow Humans" The Snoid at the Comic Book DB "The Snoid Trucks Up Broadway," music inspired by the Snoid, composed by Michael Starobin

Saddle (artwork)

Saddle is a 1993 surrealist sculpture by Irish artist Dorothy Cross. It is in the collection of the Irish Museum of Modern Art having been acquired in 1994, it is created by the combination of found objects - a metal frame, a horse's saddle and an upturned cow's udder. Virgin's Shroud, another work by Cross from 1993 features cow's udders and is in the collection of the Tate, it was no surprise to soon come upon the Freudian play of Dorothy Cross’ Saddle... There is something doubly unsettling about udders. On the one hand they remind me of large elongated nipples, which they are, on the other they have a resemblance of a small thick penis; the Saddle has a reference to the arse and so, all in all, the piece has a fascinating desire to confuse and unsettle, to engage and perturb