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The Audion is an electronic amplifier device invented by Lee De Forest in 1906. It was the forerunner of what is generally known as a triode today, in which the flow of current from the filament to the plate was controlled by a third element, the grid. A small amount of power applied to the grid could control a larger current flowing from the filament to the plate, allowing the Audion to both "detect" radio signals (that is, make them audible) and to provide a modest amount of amplification. However, De Forest's Audion is quite distinct from the true vacuum triode in that it is not capable of linear amplification. Image File history File links Size of this preview: 800 × 548 pixelsFull resolution (1835 × 1258 pixel, file size: 194 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Triode Lee De Forest Audion tube...
Image File history File links Size of this preview: 800 × 548 pixelsFull resolution (1835 × 1258 pixel, file size: 194 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Triode Lee De Forest Audion tube...
For the British rock band of the same name, see Amplifier (band). ...
Lee De Forest, (August 26, 1873 – June 30, 1961) was an American inventor with over 300 patents to his credit. ...
1906 (MCMVI) was a common year starting on Monday (see link for calendar). ...
Simplified diagram of a triode. ...
HEROW!!! A filament of a 60-watt light bulb at 75X magnification An electrical filament is a thread of metal, usually tungsten, which is used to convert electricity into heat and light for the incandescent light bulb as made in 1878 by Joseph Wilson Swan, among others. ...
Diagram of Vacuum-Tube Diode A plate is a type of electrode that formed part of a vacuum tube. ...
It has been suggested that this article or section be merged into electricity. ...
The word linear comes from the Latin word linearis, which means created by lines. ...
History It had been known since the middle of the 19th century that gas flames were electrically conductive, and early wireless experimenters had noticed that this conductivity was affected by the presence of radio waves. De Forest found that gas in a partial vacuum heated by a conventional lamp filament behaved much the same way, and that if a wire was wrapped around the glass housing, the device could serve as a detector of radio signals. In his original design, a small metal plate was sealed into the lamp housing, and this was connected to the positive terminal of a 22 volt battery via a pair of headphones, the negative terminal being connected to one side of the lamp filament. When wireless signals were applied to the wire wrapped around the outside of the glass, they caused disturbances in the current flow which produced sounds in the headphones. Conduction is the movement of electrically charged particles through a transmission medium (electrical conductor). ...
It has been suggested that this article or section be merged with Radio waves. ...
Look up Vacuum in Wiktionary, the free dictionary. ...
This was a significant development as existing commercial wireless systems were heavily protected by patents; a new type of detector would allow De Forest to market his own system. He eventually discovered that connecting the antenna circuit to a third electrode placed directly in the current path greatly improved the sensitivity; in his earliest versions, this was simply a piece of wire bent into the shape of a grid-iron (hence "grid"). For other uses, see Patent (disambiguation). ...
Compared to all competing devices at the time, the Audion was unique in that it did not draw significant power from antenna/tuned circuit, which allowed the tuning circuitry to operate with maximum selectivity. With virtually all other systems, all of the power to operate the headphones had to come from the antenna circuit itself, which tended to "damp" the tuned circuits, limiting their ability to separate stations.
Patents and disputes Arguments still continue about whether De Forest really invented the vacuum tube. What is apparent is that he (and everybody else at the time) greatly underestimated the potential of his original device, imagining it to have mostly limited military applications. It is significant that he apparently never saw its potential as a telephone repeater amplifier, even though crude electromechanical "note magnifiers" had been the bane of the telephone industry for at least two decades. (In fact, for several years it was only this "loophole" that allowed vacuum triodes to be manufactured at all, since none of the original patents specifically mentioned this application.)
De Forest was granted a patent for his early two-electrode version of the Audion on November 13, 1906 (U.S. Patent 841,386 ), but the "triode" (three electrode) version was patented in 1908 (U.S. Patent 879,532 ). De Forest continued to claim that he developed the Audion independently from John Ambrose Fleming's earlier research on the thermionic valve (for which he received Great Britain patent 24850 and the American Fleming valve patent (U.S. Patent 803,684 )), and became embroiled in many radio-related patent disputes. De Forest was famous for saying that he "didn't know why it worked, it just did". He always referred to the vacuum triodes developed by other researchers as "Oscillaudions", although there is no evidence that he had any significant input to their development. is the 317th day of the year (318th in leap years) in the Gregorian calendar. ...
1906 (MCMVI) was a common year starting on Monday (see link for calendar). ...
Sir John Ambrose Fleming (November 29, 1849 - April 18, 1945) was an English electrical engineer and physicist. ...
In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ...
Fleming valve schematic from US Patent 803,684. ...
In 1914 Edwin Armstrong published an explanation of the Audion, and when the two later faced each other in a dispute over the regeneration patent, Armstrong was able to demonstrate conclusively that De Forest still had no idea how it worked. Year 1914 (MCMXIV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ...
Edwin Howard Armstrong (December 18, 1890 – January 31, 1954) was an American electrical engineer and inventor. ...
The regenerative circuit (or self-regenerative circuit) allows a signal to be amplified many times by the same vacuum tube or other active component such as a field effect transistor. ...
The problem was that (possibly to distance his invention from the Fleming valve) De Forest's original patents specified that low-pressure gas inside the Audion was essential to its operation (Audion being a contraction of "Audio-Ion"), and in fact early Audions had severe reliability problems due to this gas being absorbed by the metal electrodes. The Audions sometimes worked extremely well; at other times they would barely work at all.
As well as De Forest himself, numerous researchers had tried to find ways to improve the reliability of the device by stabilizing the partial vacuum. One of these, Dr Irving Langmuir of General Electric, took a somewhat unorthodox approach: instead of trying to prevent the absorption of the gas, he deliberately started out with a higher vacuum and looked for ways of making the Audion work under those conditions. He succeeded, but quickly realized that, though superficially similar to the Audion, his "vacuum" tube was really a completely different device, capable of linear amplification and at much higher frequencies. Irving Langmuir at home (c. ...
“GE†redirects here. ...
One of the major weakness of De Forest's claims is that true vacuum triodes simply will not work if there is any trace of gas left in the envelope. In fact, before vacuum tubes could become commercially viable, quite elaborate techniques had to be developed to both initially evacuate the tubes and soak up any gas molecules that subsequently found their way into it. This flies directly in the face of his original patent specification, which specifically states that gas is essential to the operation of the Audion. Or does it??? If one reads the original patent 879532 dated FEB 18th 1908, DeForest states "twenty two" times in the patent one of the critical items for the audion is in fact an "evacuated vessel", to wit, a vacuum. Granted the means of producing a good vacuum in the early 1900's may have left something to be desired. Again reading the patent one finds no reference to "gas" perse as being an essential item for the audions operation, however, DeForest does mention "gaseous medium" twice. Could what he is trying to describe with the words "gaseous medium" actually be "the flow of electrons in a vacuum", as we know it today? "Gaseous medium" being used by DeForest for lack of better phraseology and understanding back then. Keeping in mind that at this time in our technological history, the early 1900's, that certain principles, wordings, phrases, understandings, were not clearly understood, documented, defined, nor were there standard phraseologies. DeForest even states in his patent that an explanation of the sensitiveness of his audion would at best be "merely tentative". Reading the actual patent (PDF link sited earlier) can give one a real insight, also taking into account the time frame of the early 1900's.
Another weakness is that none of his Audion schematics denoted the provision for any sort of "grid bias", an essential feature of any true vacuum triode operation.
Unlike the Audion, the vacuum triode could not demodulate radio signals directly (although Langmuir and other researchers soon found alternative ways to do this), but it was capable of linear (i.e. undistorted) amplification, which turned out to be a vastly more useful feature. It is ironic that many "faulty" Audions, which had lost their ability to demodulate radio signals due to gas absorption, had actually turned into crude linear amplifiers (which was why they lost their demodulating ability), but nobody realized this at the time. Demodulation is the act of removing the modulation from an analog signal. ...
Applications and use De Forest continued to manufacture and supply Audions to the US Navy up until the early 1920s, for maintenance of existing equipment, but elsewhere they were regarded as well and truly obsolete by then. It was the vacuum triode that made practical radio broadcasts a reality. Simplified diagram of a triode. ...
Prior to the introduction of the Audion radio receivers had used a variety of detectors including coherers, barretters, and crystal detectors The most popular crystal detector consisted of a small piece of galena crystal probed by a fine wire commonly referred to as a "cat's-whisker detector". They were very unreliable, requiring frequent adjustment of the cat's whisker and offered no amplification. Such systems usually required the user to listen to the signal though headphones, sometimes at very low volume, as the only energy available to operate the headphones was that picked up by the antenna. For long distance communication huge antennas were normally required, and enormous amounts of electrical power had to be fed into the transmitter. A detector is a device that recovers information of interest contained in a modulated wave. ...
The coherer was the first device used to detect radio signals in wireless telegraphy. ...
The Hot wire barretter was a demodulating detector invented in 1902 by Reginald Fessenden that found limited use in early radio receivers. ...
A cats whisker is the tiny wire that connects to the detector in a crystal radio. ...
Galena is a lead ore. ...
Cat Whisker Detector A crystal detector in commercial form from the 1960s Cat’s whisker refers to a thin wire that lightly touches a semiconducting crystal to make an imperfect contact-junction detector in a crystal radio. ...
The Audion was a considerable improvement on this, but the original devices could not provide any subsequent amplification to what was produced in the signal detection process. The later vacuum triodes allowed the signal to be amplified to any desired level, typically by feeding the amplified output of from triode into the grid of the next, eventually providing more than enough power to drive a full-sized speaker. Apart from this, they were able to amplify the incoming radio signals prior to the detection process, making it work much more efficiently.
Vacuum tubes could also be used to make superior radio transmitters. The combination of much more efficient transmitters and much more sensitive receivers revolutionized radio communication during World War I. In communications and information processing, a transmitter (sometimes abbreviated XMTR) is an object (source) which sends information to an observer (receiver). ...
“The Great War †redirects here. ...
By the late 1920s such "tube radios" began to become a fixture of most Western world households, and remained so until the introduction of transistor radios in the mid 1950s. The term Western world, the West or the Occident (Latin occidens -sunset, -west, as distinct from the Orient) [1] can have multiple meanings dependent on its context (e. ...
For other uses, see Transistor (disambiguation). ...
This does not cite any references or sources. ...
In modern electronics, the vacuum tube has been largely superseded by solid state devices such as the transistor, invented in 1947 and implemented in integrated circuits in 1959. This article is about the engineering discipline. ...
Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ...
In electronics, solid state circuits are those that do not contain vacuum tubes. ...
For other uses, see Transistor (disambiguation). ...
Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ...
See also Simplified diagram of a triode. ...
References - Radio Corp. V. Radio Engineering Laboratories, 293 U.S. 1 (United States Supreme Court 1934)
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