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A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Invented in 1906 by Lee De Forest by adding a grid to the Fleming valve, the triode was the first electronic amplification device and the ancestor of other types of vacuum tubes such as the tetrode and pentode. Its invention founded the electronics age, making possible amplified radio technology and long-distance telephony. Triodes were widely used in consumer electronics devices such as radios and televisions until the 1970s, when transistors replaced them. Today, their main remaining use is in high-power RF amplifiers in radio transmitters and industrial RF heating devices. The word is derived from the Greek τρίοδος, ''tríodos'', from ''tri-'' (three) and ''hodós'' (road, way), originally meaning the place where three roads meet. == History == The first vacuum tube, the diode or Fleming valve, which had two electrodes, a filament and a plate (anode), was invented by John Ambrose Fleming in 1904 as a radio receiver detector. The first three-element tube, a mercury-vapor-filled tube with a control grid, was patented on March 4, 1906, by the Austrian Robert von Lieben.〔() DRP 179807〕〔Tapan K. Sarkar (ed.) "History of wireless", John Wiley and Sons, 2006. ISBN 0-471-71814-9, p.335〕〔Sōgo Okamura (ed), ''History of Electron Tubes'', IOS Press, 1994 ISBN 90-5199-145-2 page 20〕 Independently, beginning in 1906,〔() Patent US841387 from 10/25/1906〕〔(U.S. Patent 879,532 )〕 American engineer Lee De Forest invented a number of three-element tube designs by adding an electrode to the diode, which he called Audions.〔 The link is to a reprint of the paper in the ''Scientific American Supplement, No. 1665, November 30, 1907, p.348-350, copied on Thomas H. White's (United States Early Radio History ) website〕 The Audion is considered the first triode. 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.〔, ''( Space Telegraphy )'', filed January 29, 1907, issued February 18, 1908〕 The Audion was incompletely evacuated and contained some gas at low pressure, thought to be necessary by De Forest, which caused erratic operation and shortened the life of the filament.〔〔 Invented as a radio receiver detector,〔 the Audion did not see much use until its ability to amplify was recognized around 1912 by several researchers,〔 who used it to build the first successful amplifying radio receivers and electronic oscillators.〔〔. Republished as 〕 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",〔〔 These were the first vacuum tube triodes.〔 The name triode appeared later, when it became necessary to distinguish it from other kinds of vacuum tubes with more or fewer elements (e.g. diodes, tetrodes, pentodes, etc.). There were lengthy lawsuits between De Forest and von Lieben, and De Forest and the Marconi Company, representing John Ambrose Fleming who invented the diode. The discovery of the triode's amplifying ability in 1912 revolutionized electrical technology, creating the new field of ''electronics'', the technology of active (amplifying) electrical devices. The triode was immediately applied to many areas of communication. Triode "continuous wave" radio transmitters replaced the cumbersome inefficient "damped wave" spark gap transmitters, allowing the transmission of sound by amplitude modulation (AM). Amplifying triode radio receivers, which had the power to drive loudspeakers, replaced weak crystal radios, 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 repeaters, invented at 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 systems, electric phonographs, and talking motion pictures. The triode served as the technological base from which later vacuum tubes developed, such as the tetrode (Walter Schottky, 1916) and pentode (Bernardus 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 systems until it was replaced in the 1960s by the transistor, invented in 1947, which brought the "vacuum tube" era started by the triode to a close. Today triodes are mostly used in high-power applications for which solid state semiconductor devices 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「triode」の詳細全文を読む スポンサード リンク
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