Triode Audion vacuum tube from 1908. The filament (which was also the cathode) was at the lower left inside the tube, but has burned out and is no longer present. The filament's connecting and supporting wires are visible. The plate is at the middle top, and the grid is the serpentine electrode below it. The plate and grid connections leave the tube at the right.
The Audion was an electronic detecting or amplifying vacuum tube[1] invented by American electrical engineer Lee de Forest as a diode in 1906.[2][3][4][5] Improved, it was patented as the first triode in 1908,[1][6][7][8][9] consisting of an evacuated glass tube containing three electrodes: a heated filament (the cathode, made out of tantalum), a grid, and a plate (the anode).[4] It is important in the history of technology because it was the first widely used electronic device which could amplify.[4] A low power signal at the grid could control much more power in the plate circuit.
Audions had more residual gas than later vacuum tubes; the residual gas limited the dynamic range and gave the Audion non-linear characteristics and erratic performance.[1][8] Originally developed as a radio receiver detector[3] by adding a grid electrode to the Fleming valve, it found little use until its amplifying ability was recognized around 1912 by several researchers,[8][10] who used it to build the first amplifying radio receivers and electronic oscillators.[9][11] The many practical applications for amplification motivated its rapid development, and the original Audion was superseded within a few years by improved versions with a higher vacuum.[8][10]
^ abcOkamura, Sōgo (1994). History of Electron Tubes. IOS Press. pp. 17–22. ISBN 9051991452.
^De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is U.S. patent 879,532, Space Telegraphy, filed January 29, 1907, issued February 18, 1908
^ abde Forest, Lee (January 1906). "The Audion; A New Receiver for Wireless Telegraphy". Trans. AIEE. 25. American Institute of Electrical and Electronics Engineers: 735–763. doi:10.1109/t-aiee.1906.4764762. Retrieved March 30, 2021. 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.
^ abcGodfrey, Donald G. (1998). "Audion". Historical Dictionary of American Radio. Greenwood Publishing Group. p. 28. ISBN 9780313296369. Retrieved January 7, 2013.
^de Forest, Lee (30 Nov 1907). "The Audion - A new receiver for wireless telegraphy". Scientific American. 64 (1665): 348–352. Retrieved 21 October 2023. Non-paywalled reprint of the DeForest presentation at the October 26, 1906 New York meeting of the AIEE. Text version available at the Early Radio History site.
^Amos, S. W. (2002). "Triode". Newnes Dictionary of Electronics, 4th Ed. Newnes. p. 331. ISBN 9780080524054. Retrieved January 7, 2013.
^Hijiya, James A. (1992). Lee de Forest. Lehigh University Press. p. 77. ISBN 0934223238.
^ abcdLee, Thomas H. (2004). Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits. Cambridge University Press. pp. 13–14. ISBN 0521835267.
^ abHempstead, Colin; Worthington, William E. (2005). Encyclopedia of 20th-Century Technology, Vol. 2. Taylor & Francis. p. 643. ISBN 1579584640.
^ abNebeker, Frederik (2009). Dawn of the Electronic Age: Electrical Technologies in the Shaping of the Modern World, 1914 to 1945. John Wiley & Sons. pp. 14–15. ISBN 978-0470409749.
^Armstrong, E. H. (September 1915). "Some Recent Developments in the Audion Receiver". Proceedings of the IRE. 3 (9): 215–247. doi:10.1109/jrproc.1915.216677. S2CID 2116636.. Republished as Armstrong, E. H. (April 1997). "Some Recent Developments in the Audion Receiver" (PDF). Proceedings of the IEEE. 85 (4): 685–697. doi:10.1109/jproc.1997.573757.
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