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see electron tubeelectron tube,
device consisting of a sealed enclosure in which electrons flow between electrodes separated either by a vacuum (in a vacuum tube) or by an ionized gas at low pressure (in a gas tube).
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an electron tube with three electrodes, namely, a directly or indirectly heated cathode, a control grid, and an anode, or plate. The triode was invented in 1906 by L. De Forest. At first, triodes were used only as receiver tubes. In 1913 the German scientist A. Meissner showed that the triode could be used as an oscillator tube.

In the simplest triode, a helical grid is placed inside a cylindrical plate. Both the plate and the grid are usually made of a refractory metal, such as Ni, Mo, or Ta. The cathode is located on the common axis of the plate and the grid and is made of pure tungsten or thoriated tungsten carbide or may be oxide coated. The designs and the values of the parameters of currently used triodes vary widely and are determined mainly by the intended use. For example, triodes used in the initial stages of amplifiers and in voltage regulators have a high amplification factor of 30–100. Triodes used in output amplifier stages and in current regulators have a grid-plate characteristic whose linear section is shifted to the left, a low amplification factor of 4–10, and a relatively high plate dissipation of up to 20 watts. Triodes that amplify high-frequency oscillations, particularly in cascades with a common (grounded) grid, have a very steep grid-plate characteristic and a low plate-cathode capacitance.

Receiver triodes are often built as combined units, in which the same bulb contains two or more systems of electrodes; examples include duotriodes, diode-triodes, and triode-pentodes. Nuvi-stors and miniaturized triodes with rigid or flexible leads have come into use. Cermets are used in triodes intended for operation at frequencies above 1 gigahertz; such triodes have a system of planar electrodes and annular leads (to facilitate connection to external resonators or wave guides). Oscillator triodes and modulator triodes (the latter having a lower amplification factor than the former and a grid-plate characteristic whose linear section lies to the left of the plate-current zero axis) have different plate-dissipation capacities and, consequently, different useful output powers. Thus, in triodes with glass envelopes and natural cooling, the useful output power may be as high as several kilowatts; in triodes with an external plate that is a part of the vacuum envelope and with forced-air or liquid cooling, the useful output power reaches 1 megawatt. Triodes intended for pulse operation are characterized by a high pulsed cathode emission capacity and a large useful (pulsed) output of several hundred kilowatts with a negligible mean plate dissipation.

With the development of semiconductor electronics, triodes have been largely supplanted by semiconductor devices. Triodes have retained their importance, however, in a number of devices, for example, high-power oscillators and radio receivers intended for operation at high radiation levels and over broad temperature ranges.


Kleiner E. Iu. Osnovy teorii elektronnykh lamp. Moscow, 1974.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A three-electrode electron tube containing an anode, a cathode, and a control electrode.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A type of vacuum tube that is used in audio and radio amplifiers and oscillator circuits. It is like a diode with the addition of a wire mesh control grid between the cathode and plate (anode) that controls current flow. A filament heats the cathode enabling it to release electrons. When a small voltage is applied to the grid, the current flow between the cathode and plate is changed accordingly. In some triodes, the filament is the cathode. See diode, tetrode and magnetron.

The Triode Uses a Grid
Adding a control grid to the diode allows the current to be varied between the cathode and anode.
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References in periodicals archive ?
(Raven, English I) The other participants didn't report having thought about OCF effectiveness; hence, we could not identify clear triodes for this aspect of OCF.
Possible Triodes That Arise From the Combination of the Three Attitudinal Components (Jain, 2014) TRIODE Affective Conative Cognitive ppp Positive Positive Positive PPN Positive Positive Negative PNP Positive Negative Positive PNN Positive Negative Negative NPP Negative Positive Positive NPN Negative Positive Negative NNP Negative Negative Positive NNN Negative Negative Negative
(268) Lee De Forest, a leading inventor of radio technology, patented a substantial improvement, the oscillating triode, which amplified electrical signals and thus exhibited much greater sensitivity in radio reception.
(269.) As an indication of the importance of De Forest's invention, the triode has been called "the heart and soul of radio." GEORGE H.
The inventors expect the triode to operate under conditions of radiation or heat that would make standard semiconductor components fail.
In a triode, on the other hand, a third filament called a grid lies between the cathode and anode.
The main advantages of semiconductor triodes over vacuum ELs are [16, 17]:
* high reliability in operation and great mechanical strength to shock loads and vibrations of individual semiconductor triodes and an electronic device as a whole containing a huge number of similar semiconductor devices;
Pulsed diodes, radiation diodes, surface ionization triodes, and ion dispenser triodes are all variations of the vapor filled thermionic converter.
An even smaller faction of those who "think tribes" have entered into the world of single-ended triode amplifiers (SETs) and extremely efficient horn loudspeakers, maintaining that these amplifiers offer the purest, most accurate, sound possible.
Vacuum electronics technology embraces a wide range of devices, including the traditional multiterminal vacuum tubes, such as triodes, pentodes and beam power tubes, as well as many linear-beam and crossed-field devices, which employ either slow- or fast-wave structures, such as TWTs, klystrons, backward-wave amplifiers and oscillators, gyrotrons, free electron lasers and Cerenkov devices.
Other applications are offset bombing beacons and rendezvous beacons for refueling operations, for replacement of magnetrons at X- and Ku-bands and vacuum tube triodes at C-band.