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Triode

 
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Triode
 
 
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A triode is an electronic amplification
Amplifier

Generally, an amplifier or simply amp, is any machine that changes, usually increases, the amplitude of a Signal . The "signal" is usually voltage or current....
 device having three active electrodes. The term most commonly applies to a vacuum tube
Vacuum tube

In electronics, a vacuum tube, electron tube , thermionic valve, or just valve is a device used to amplifier, switch, otherwise modify, or create an Electricity signal by controlling the movement of electrons in a low-pressure space....
 (or valve in British English) with three elements: the filament or cathode
Cathode

A cathode is an electrode through which electric charge flows out of a polarized electrical device. Mnemonic: CCD .From an electrochemical point of view, positively charged ion invariably move toward the cathode and/or negatively charged ion move away from it to balance the electrons arriving from external circuitry....
, the grid
Control grid

The control grid is an electrode used in vacuum tube used to modulate the flow of electrons in the cathode to anode or plate electrode circuit....
, and the plate
Plate electrode

See anode.A plate is a type of electrode that formed part of a vacuum tube. The plate is impressed with a positive charge so that it may capture and flow electrons within a circuit....
 or anode
Anode

An anode is an electrode through which electric charge flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the positive electric current....
. The triode vacuum tube is the first electronic amplification
Electronic amplifier

An electronic amplifier is a device for increasing the Power and/or amplitude of a Signal . It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude....
 device.

original three-element device was patented in 1908 by Lee De Forest
Lee De Forest

Lee De Forest was an United States inventor with over 180 patents to his credit. De Forest invented the Audion tube, a vacuum tube that takes relatively weak electrical signals and amplifies them....
 who developed it from his original two-element 1906 Audion
Audion tube

The Audion is an electronic amplifier device invented by Lee De Forest in 1906. It was the forerunner of the triode, in which the current from the Electrical filament to the Plate electrode was controlled by a third element, the grid....
.






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Encyclopedia


Triode
A triode is an electronic amplification
Amplifier

Generally, an amplifier or simply amp, is any machine that changes, usually increases, the amplitude of a Signal . The "signal" is usually voltage or current....
 device having three active electrodes. The term most commonly applies to a vacuum tube
Vacuum tube

In electronics, a vacuum tube, electron tube , thermionic valve, or just valve is a device used to amplifier, switch, otherwise modify, or create an Electricity signal by controlling the movement of electrons in a low-pressure space....
 (or valve in British English) with three elements: the filament or cathode
Cathode

A cathode is an electrode through which electric charge flows out of a polarized electrical device. Mnemonic: CCD .From an electrochemical point of view, positively charged ion invariably move toward the cathode and/or negatively charged ion move away from it to balance the electrons arriving from external circuitry....
, the grid
Control grid

The control grid is an electrode used in vacuum tube used to modulate the flow of electrons in the cathode to anode or plate electrode circuit....
, and the plate
Plate electrode

See anode.A plate is a type of electrode that formed part of a vacuum tube. The plate is impressed with a positive charge so that it may capture and flow electrons within a circuit....
 or anode
Anode

An anode is an electrode through which electric charge flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the positive electric current....
. The triode vacuum tube is the first electronic amplification
Electronic amplifier

An electronic amplifier is a device for increasing the Power and/or amplitude of a Signal . It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude....
 device.

Invention

The original three-element device was patented in 1908 by Lee De Forest
Lee De Forest

Lee De Forest was an United States inventor with over 180 patents to his credit. De Forest invented the Audion tube, a vacuum tube that takes relatively weak electrical signals and amplifies them....
 who developed it from his original two-element 1906 Audion
Audion tube

The Audion is an electronic amplifier device invented by Lee De Forest in 1906. It was the forerunner of the triode, in which the current from the Electrical filament to the Plate electrode was controlled by a third element, the grid....
. The Audion did provide amplification. However it was not until around 1912 that other researchers, while attempting to improve the service life of the audion, stumbled on the principle of the true vacuum tube. The name triode appeared later, when it became necessary to distinguish it from other generic kinds of vacuum tubes with more or less elements (eg diode
Diode

In electronics, a diode is a two-terminal device .Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional electric current property....
s, tetrode
Tetrode

A tetrode is an electronic device having four active electrodes. The term most commonly applies to a two-grid vacuum tube. It has the three electrodes of a triode and an additional screen grid which significantly changes its behaviour....
s, pentode
Pentode

A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid vacuum tube, which was invented by the Dutchman Bernard Tellegen in 1926....
s etc.). The Audion tubes deliberately contained some gas at low pressure. The name triode is only applied to vacuum tubes which have been evacuated of as much gas as possible.

Operation

The principle of its operation is that, as with a thermionic diode
Diode

In electronics, a diode is a two-terminal device .Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional electric current property....
, the heated filament causes a flow of electron
Electron

The electron is a subatomic particle that carries a negative electric charge. It has elementary particle and is believed to be a point particle....
s that are attracted to the plate and create a current. Applying a negative charge to the control grid will tend to repel some of the (also negatively charged) electrons back towards the filament: the larger the charge on the grid, the smaller the current to the plate. If an AC signal is superimposed on the DC bias of the grid, an amplified version of the AC signal appears in the plate circuit.

Applications

Although triodes are now largely obsolete in consumer electronics
Consumer electronics

Consumer electronics include electronic equipment intended for everyday use. Consumer electronics are most often used in entertainment, communications and office productivity....
, having been replaced by the transistor
Transistor

In electronics, a transistor is a semiconductor device commonly used to Electronic amplifier or switch Electronics signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit....
, triodes continue to be used in certain high-end
High-end audio

High-end audio is a term used to describe a class of consumer home audio equipment marketed to audio enthusiasts on the basis of high price or quality, and esoteric or novel sound reproduction technologies....
 and professional audio
Professional audio

Professional audio, also 'pro audio', can be used a term to refer to both a type of audio equipment as well as a type of audio engineering application....
 applications, as well as in microphone preamplifier
Preamplifier

A preamplifier , or control amp in some parts of the world, is an electronic amplifier which precedes another amplifier to prepare an electronic Signalling for further amplification or processing....
s and electric guitar amplifier
Guitar amplifier

A guitar amplifier is an electronic amplifier designed to make the signal of an electric guitar or an acoustic guitar louder and modify the tone by emphasizing or de-emphasizing certain frequencies and/or by adding electronic effects....
s.

Some guitarists routinely drive their amplifiers to the point of saturation
Saturation current

Saturation current is a term used to describe a limit to the amount of electrical current that can flow in an electronic circuit or device. As the voltage applied to a circuit is increased, the current flow will increase proportionately until the saturation current is achieved, at which point the excess current can no longer flow, and is ins...
, in order to produce a desired distortion tone. Many people prefer the sound of triodes in such an application, since the distortion of a tube amplifier, which has a "soft" saturation characteristic, can be more pleasing to the ear than that of a typical solid-state
Solid state (electronics)

Solid-state electronic components, devices, and systems are based entirely on the semiconductor, such as transistors, microprocessor chips, and the bubble memory....
 amplifier, which is linear up to the limits of its supply voltage and then clips
Clipping (audio)

Clipping is a form of waveform Distortion#Audio distortion that occurs when an amplifier is overdriven, which happens through attempts to increase the voltage or current beyond its maximum power capability....
 abruptly. However, this typically only applied to the power stage of a tube amplifier.

See also

  • Vacuum tube
    Vacuum tube

    In electronics, a vacuum tube, electron tube , thermionic valve, or just valve is a device used to amplifier, switch, otherwise modify, or create an Electricity signal by controlling the movement of electrons in a low-pressure space....
  • List of vacuum tubes
    List of vacuum tubes

    Heater or filament voltagesVacuum tubes fall into three main non-interchangeable categories according to their heater or filament voltage:# Battery types, with a low-power filament operated usually from 1 to 2V, all filaments connected in parallel....
  • European triode festival
    European triode festival

    Since 2000 each year the "European Triode Festival" has been held in various venues in Europe For the first 3 years, the festival was organised by Kurt Steffensen and held in Aarhus, Denmark....

External links

  • — A French page on thermionic valves. Of particular interest is the 17 minute video showing the manual production of triodes.