Schematic diagram of a 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 Bernhard D.H. Tellegen in 1926. Image File history File links Pentoda_symbol. ... Image File history File links Pentoda_symbol. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... Bernard D.H. Tellegen (Netherlands, 24 June 1900 - Eindhoven, 30 August 1990) was an electrical engineer and inventor of the penthode and the gyrator. ...

Advantages over tetrode

A tetrode could supply sufficient power to a speaker or transmitter, and offered a larger amplification factor than the prior art triode. A tetrode is a two-grid vacuum tube. ... Simplified diagram of a triode. ...

However, the positively charged screen grid can collect the secondary electrons emitted from the anode, which can cause increased current toward the screen grid, and cause the anode current to decrease with increasing anode voltage over part of the Ia/Va characteristic. Tellegen introduced an additional electrode, called the suppressor grid, which solved the problem of secondary emission. It does this by being held at a low potential, usually either grounded or connected to the cathode. The secondary emission still occurs, but the electrons can no longer reach the screen grid, since they have less energy than the primary electrons and hence cannot pass the grounded suppressor grid. Therefore these secondary electrons are are re-collected by the anode. Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ... A grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. ...

Usage

Pentode valves were first used in consumer-type radio receivers. A well-known pentode type, the EF-50, was designed before the start of the World War II. The EF-50 pentode was extensively used in radar sets and other military electronic equipment. The pentode contributed to the electronic preponderance of the Allies. After WW II, pentodes were widely used in TV receivers. Vacuum tubes were replaced by transistors during the 1960s. However, pentodes and triodes, known for their valve sound, still continue to be used in certain high-end and professional audio applications, as well as in microphone preamplifiers and electric guitar amplifiers. Valve sound is the sound either from a valve amplifier or a specially designed transistor amplifier. ... High-end audio is a term used to describe equipment that is purported by the manufacturers to be the best, regardless of the price. ... 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. ... An example of a typical high-end stereo preamplifier. ... This article or section does not adequately cite its references or sources. ...

See also

• Beam tetrode
• Pentode transistor