Editing Triode (section)

== History ==
===Precursor devices===
[[File:Triode tube 1906.jpg|thumb|upright=1.05|De Forest Audion tube from 1908, the first triode. The flat plate is visible on the top, with the zigzag wire grid under it. The filament was originally present under the grid but was burnt out.]]
[[File:Lieben-Reisz vacuum tube.jpg|thumb|upright=0.4|Lieben-Reisz tube, another primitive triode developed the same time as the Audion by Robert v. Lieben]]

Before thermionic valves were invented, [[Philipp Lenard]] used the principle of grid control while conducting photoelectric experiments in 1902.<ref name="Burns">{{cite book
 | last1  = Burns
 | first1 = Russell W. 
 | title  = Communications: An International History of the Formative Years
 | publisher = Institute of Electrical Engineers
 | date   = 2004
 | location = London
 | pages  = 339
 | url    = https://books.google.com/books?id=7eUUy8-VvwoC&q=Lenard+%22Grid+Control%22&pg=PA339
 | isbn   = 0863413277
 }}</ref>

The first [[vacuum tube]] used in radio<ref name="Aitken2">{{cite book
 | last1  = Aitken
 | first1 = Hugh G.J. 
 | title  = The Continuous Wave: Technology and American Radio, 1900-1932
 | publisher = Princeton University Press
 | date   = 2014
 | pages  = 195
 | url    = https://books.google.com/books?id=ebr_AwAAQBAJ&q=Fleming+valve&pg=PA195
 | isbn   = 978-1400854608
 }}</ref><ref name="Fisher">{{cite book
 | last1  = Fisher
 | first1 = David E.
 | last2  = Fisher
 | first2 = Marshall
 | title  = Tube: The Invention of Television
 | publisher = Counterpoint
 | date   = 1996
 | pages  = 54
 | url    = https://books.google.com/books?id=eApTAAAAMAAJ&q=%22first+vacuum+tube%22+fleming+valve&pg=PA54
 | isbn   = 1887178171
 }}</ref> was the [[thermionic diode]] or [[Fleming valve]], invented by [[John Ambrose Fleming]] in 1904 as a [[Detector (radio)|detector]] for [[radio receiver]]s. It was an evacuated glass bulb  containing two electrodes, a heated filament (cathode) and a plate (anode).

===Invention===
Triodes came about in 1906 when American engineer [[Lee de Forest]]<ref name="Tyne6">{{cite journal
  | last1  = Tyne
  | first1 = Gerald F. J.
  | title = The Saga of the Vacuum Tube, Part 6
  | journal = Radio News
  | volume = 30
  | issue = 3
  | pages = 26–28, 91
  | publisher = Ziff-Davis
  | location = Chicago, IL
  | date = September 1943
  | url = http://www.americanradiohistory.com/Archive-Radio-News/40s/Radio-News-1943-09.pdf
  | access-date = November 30, 2016}}</ref> and Austrian physicist [[Robert von Lieben]]<ref name="Tyne8">{{cite journal
  | last1  = Tyne
  | first1 = Gerald F. J.
  | title = The Saga of the Vacuum Tube, Part 8
  | journal = Radio News
  | volume = 30
  | issue = 5
  | pages = 26–28
  | publisher = Ziff-Davis
  | location = Chicago, IL
  | date = November 1943
  | url = http://www.americanradiohistory.com/Archive-Radio-News/40s/Radio-News-1943-11-R.pdf
  | access-date = November 30, 2016}}</ref> independently patented tubes that added a third  electrode, a [[control grid]], between the filament and plate to control current.<ref name="Anton A. Huurdeman 2003, page 226">Anton A. Huurdeman, The Worldwide History of Telecommunications, John Wiley & Sons - 2003, page 226</ref><ref>John Bray, The Communications Miracle: The Telecommunication Pioneers from Morse to the Information Superhighway, Springe - 2013, pages 64-65</ref> Von Lieben's partially-evacuated three-element tube, patented in March 1906, contained a trace of [[mercury (element)|mercury vapor]] and was intended to amplify weak telephone signals.<ref>[http://www.hts-homepage.de/Lieben/Lieben.html] DRP 179807</ref><ref>[[Tapan K. Sarkar]] (ed.) "History of wireless", John Wiley and Sons, 2006. {{ISBN|0-471-71814-9}}, p.335</ref><ref>Sōgo Okamura (ed), ''History of Electron Tubes'', IOS Press, 1994 {{ISBN|90-5199-145-2}} page 20</ref><ref name="Tyne8" /> Starting in October 1906<ref name="Anton A. Huurdeman 2003, page 226"/> De Forest patented a number of three-element tube designs by adding an electrode to the diode, which he called [[Audion]]s, intended to be used as radio detectors.<ref name="De Forest">{{cite journal
  | last = De Forest
  | first = Lee
  | title = The Audion; A New Receiver for Wireless Telegraphy
  | journal = Trans. AIEE
  | volume = 25
  | pages = 735–763
  | publisher = American Institute of Electrical and Electronics Engineers
  | date = January 1906
  | url = https://babel.hathitrust.org/cgi/pt?id=uiug.30112089533605&view=1up&seq=356
  | doi = 10.1109/t-aiee.1906.4764762
  | access-date = March 30, 2021| url-access = subscription
  }} The link is to a reprint of the paper in the ''Scientific American Supplement'', Nos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350 and 354-356</ref><ref name="Tyne6" /> The one which became the design of the triode, in which the grid was located between the filament and plate, was patented January 29, 1907.<ref name="AudionPatent" >{{US patent|879532}}, ''[https://patents.google.com/patent/US879532 Space Telegraphy]'', filed January 29, 1907, issued February 18, 1908</ref><ref name="Tyne6" /><ref name="Hijiya">{{cite book
 | last1  = Hijiya
 | first1 =  James A. 
 | title  = Lee de Forest and the Fatherhood of Radio
 | publisher = Lehigh University Press
 | date   = 1997
 | pages  = 77
 | url    = https://books.google.com/books?id=JYylHhmoNZ4C&q=%22+audion+%22+1907&pg=PA77
 | isbn   = 0934223238
 }}</ref> Like the von Lieben vacuum tube, De Forest's Audions were incompletely evacuated and contained some gas at low pressure.<ref name="Okamura">{{cite book
  | last = Okamura
  | first = Sōgo 
  | title = History of Electron Tubes
  | publisher = IOS Press
  | year = 1994
  | pages = 17–22
  | url = https://books.google.com/books?id=VHFyngmO95YC&q=Audion+triode&pg=PA21
  | isbn = 9051991452}}</ref><ref name="Lee">{{cite book
  | last = Lee
  | first = Thomas H. 
  | title = Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits
  | publisher = Cambridge University Press
  | year = 2004
  | pages = 13–14
  | url = https://books.google.com/books?id=uoj3IWFxbVYC&q=Audion+triode&pg=PA13
  | isbn = 0521835267}}</ref> von Lieben's vacuum tube did not see much development due to his death seven years after its invention, shortly before the outbreak of the [[First World War]].<ref>John Bray, The Communications Miracle: The Telecommunication Pioneers from Morse to the Information Superhighway, Springe - 2013, page 64</ref>

De Forest's Audion did not see much use until its ability to amplify was recognized around 1912 by several researchers,<ref name="Lee" /><ref name="Nebeker">{{cite book
  | last = Nebeker
  | first = Frederik
  | title = Dawn of the Electronic Age: Electrical Technologies in the Shaping of the Modern World, 1914 to 1945
  | publisher = John Wiley & Sons
  | year = 2009
  | pages = 14–15
  | url = https://books.google.com/books?id=xwmH6-q5O5AC&q=nebeker+audion+%22De+forest&pg=PA14
  | isbn = 978-0470409749}}</ref> who used it to build the first successful amplifying radio receivers and [[electronic oscillator]]s.<ref name="Hempstead">{{cite book
  | last = Hempstead
  | first = Colin
  |author2=William E. Worthington
   | title = Encyclopedia of 20th-Century Technology, Vol. 2
  | publisher = Taylor & Francis
  | year = 2005
  | pages = 643
  | url = https://books.google.com/books?id=0wkIlnNjDWcC&q=%22H+J+triode%22+audion&pg=PA648
  | isbn = 1579584640}}</ref><ref name="Armstrong1915">{{cite journal
|last=Armstrong
|first=E.H.
|author-link=Edwin Howard Armstrong
|pages=215–247
|title=Some Recent Developments in the Audion Receiver 
|journal=Proceedings of the IRE 
|volume=3 
|number=9 
|date=September 1915
|doi=10.1109/jrproc.1915.216677|s2cid=2116636
|url=https://zenodo.org/record/1432482
}}. Republished as {{cite journal 
|last=Armstrong 
|first=E.H. 
|author-link=Edwin Howard Armstrong 
|title=Some Recent Developments in the Audion Receiver 
|journal=Proceedings of the IEEE 
|volume=85 
|number=4 
|date=April 1997
|url=http://www.ieee.org/documents/00573757.pdf 
|pages=685–697
|doi=10.1109/jproc.1997.573757}}</ref> The many uses for amplification motivated its rapid development. By 1913 improved versions with higher vacuum were developed by Harold Arnold at [[American Telephone and Telegraph Company]], which had purchased the rights to the Audion from De Forest, and [[Irving Langmuir]] at [[General Electric]], who named his tube the "Pliotron",<ref name="Lee" /><ref name="Nebeker" /> These were the first [[vacuum tube]] triodes.<ref name="Okamura" /> The name "triode" appeared later, when it became necessary to distinguish it from other kinds of vacuum tubes with more or fewer elements ([[Diode#Vacuum tube diodes|diode]]s, [[tetrode]]s, [[pentode]]s, etc.). There were lengthy lawsuits between De Forest and von Lieben, and De Forest and the [[Marconi Company]], who represented [[John Ambrose Fleming]], the inventor of the diode.<ref name=Hijiya92 >James A. Hijiya, ''Lee de Forest and the Fatherhood of Radio Political, and Economic Development '' Lehigh University Press, 1992. {{ISBN|0934223238}}, pages 93-94</ref>

===Wider adoption===
The discovery of the triode's amplifying ability in 1912 revolutionized electrical technology, creating the new field of ''[[electronics]]'',<ref name="Nebeker" /> the technology of [[passivity (engineering)|active]] ([[amplifier|amplifying]]) electrical devices. The triode was immediately applied to many areas of communication. During World War I, [[amplitude modulation|AM]] voice [[two way radio]] sets were made possible in 1917 (see [[TM (triode)]]) which were simple enough that the pilot in a single seat aircraft could use it while flying. Triode "[[continuous wave]]" [[transmitter|radio transmitters]] replaced the cumbersome inefficient "[[Damped wave (radio transmission)|damped wave]]" [[spark-gap transmitter]]s, allowing the transmission of sound by [[amplitude modulation]] (AM). Amplifying triode [[radio receiver]]s, which had the power to drive [[loudspeaker]]s, replaced weak [[crystal radio]]s, which had to be listened to with [[earphones]], allowing families to listen together. This resulted in the evolution of radio from a commercial message service to the first [[mass communication]] medium, with the beginning of [[radio broadcasting]] around 1920. Triodes made transcontinental telephone service possible. Vacuum tube triode [[repeater]]s, invented at [[AT&T|Bell Telephone]] after its purchase of the Audion rights, allowed telephone calls to travel beyond the unamplified limit of about 800 miles. The opening by Bell of the first transcontinental telephone line was celebrated 3 years later, on January 25, 1915. Other inventions made possible by the triode were [[television]], [[public address system]]s, electric [[phonograph]]s, and [[talking motion picture]]s.

The triode served as the technological base from which later vacuum tubes developed, such as the [[tetrode]] ([[Walter Schottky]], 1916) and [[pentode]] (Gilles Holst and Bernardus Dominicus Hubertus Tellegen, 1926), which remedied some of the shortcomings of the triode detailed below.

The triode was very widely used in [[consumer electronics]] such as radios, televisions, and [[audio system]]s until it was replaced in the 1960s by the [[transistor]], invented in 1947, which brought the "vacuum tube era" introduced by the triode to a close.  Today triodes are used mostly in high-power applications for which solid state [[semiconductor device]]s are unsuitable, such as radio transmitters and industrial heating equipment. However, more recently the triode and other vacuum tube devices have been experiencing a resurgence and comeback in high fidelity audio and musical equipment.  They also remain in use as vacuum fluorescent displays (VFDs), which come in a variety of implementations but all are essentially triode devices.