Structure of a vacuum tube triode

A triode is an electronic amplification device having three active electrodes. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. The term most commonly applies to a vacuum tube (or valve in British English) with three elements: the filament or cathode, the grid, and the plate or anode. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. An electrical filament is a thread of Metal, usually Tungsten, which is used to convert Electricity into light in Incandescent light bulbs (as developed A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device The control grid is an Electrode used in thermionic valves (vacuum tubes used to modulate the flow of electrons in the Cathode to Anode or See Anode.A plate is a type of Electrode that formed part of a Vacuum tube. An anode is an Electrode through which Electric current flows into a polarized electrical device The triode vacuum tube is often viewed as the first electrical amplification device, although the relay (which contained mechanical parts) is usually viewed, in a broad sense, as the first actual electrical amplifier. A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal.

Invention

Lee De Forest "Triode" Audion tube from 1908

The original three-element device was patented in 1908 by Lee De Forest who developed it from his original two-element 1906 Audion. Year 1908 ( MCMVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year Lee De Forest, ( August 26, 1873 – June 30, 1961) was an American Inventor with over 300 patents to his credit The Audion is an electronic Amplifier device invented by Lee De Forest in 1906 The Audion did incorporate, in a crude form, the key principle of allowing 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 diodes, tetrodes, pentodes etc. Dioden2jpg|thumb|right|150px|Figure 2 Various semiconductor diodes A tetrode is an electronic device having four active Electrodes The term most commonly applies to a two-grid Vacuum tube. 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 ). The original Audion tubes were not vacuum tubes however, as they deliberately contained some gas at low pressure. The name triode is only applied to vacuum tubes.

Operation

Schematic symbol for an indirectly heated triode.

The principle of its operation is that, as with a thermionic diode, the heated filament causes a flow of electrons that are attracted to the plate and create a current flow. Dioden2jpg|thumb|right|150px|Figure 2 Various semiconductor diodes The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J 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 flow 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, having been replaced by the transistor, triodes continue to be used in certain high-end and professional audio applications, as well as in microphone preamplifiers and electric guitar amplifiers. Consumer electronics include electronic equipment intended for everyday use In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals High-end audio is a term used to describe higher priced and/or higher quality audio equipment 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 A preamplifier (preamp or control amp in some parts of the world is an Electronic amplifier which precedes another amplifier to prepare an electronic A guitar amplifier is an Electronic amplifier designed for use with an electric or electronic Musical instrument, such as an Electric guitar.

Some guitarists routinely drive their amplifiers to the point of saturation, in order to produce a desired distortion tone. Saturation current is a term used to describe a limit to the amount of current that can flow in an Electronic circuit or device 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 amplifier, which is linear up to the limits of its supply voltage and then clips abruptly. Solid-state Electronic components devices and systems are based entirely on the Semiconductor, such as Transistors Microprocessor chips and Clipping is a form of Waveform distortion that occurs when an Amplifier is overdriven which happens through attempts to increase the voltage or current However, this typically only applied to the power stage of a tube amplifier.

External links

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

See also

• Vacuum tube
• List of vacuum tubes
• European triode festival