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» Vacuum tubes by types » Pentodes, Tetrodes
Pentodes, Tetrodes
A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid amplifying vacuum tube (thermionic valve), which was invented by the Dutchman Bernhard D.H. Tellegen in 1926. The pentode consists of an evacuated glass envelope containing five electrodes in this order: a cathode heated by a filament, a control grid, a screen grid, a suppressor grid, and a plate (anode). The pentode (called a "triple-grid amplifier" in some early literature) was developed from the tetrode tube by the addition of a third grid, the suppressor grid. This served to prevent secondary emission electrons emitted by the plate from reaching the screen grid, which caused instability and parasitic oscillations in the tetrode. The pentode is closely related to the beam tetrode. Pentodes were widely used in industrial and consumer electronic equipment such as radios and televisions until the 1960s, when they were replaced by transistors. Their main use now is in high power industrial applications such as radio transmitters. The obsolete consumer tubes are still used in a few legacy and specialty vacuum tube audio devices.
Output pentode, Beam tetrode Sharp-cutoff pentode Variable-mu, Remote-cutoff pentode
Double pentode, Double tetrode Tetrode
6AU6 / EF94 / 6J4P / 6Zh4P tube
EF80 / 6BX6 TELAM tube
GU-81M / GU81M / GU-81 700W 50MHz pentode tube
EF861 RFT GOLD pin tube
1P2B / 507 MELZ output pentode tube
6J10B-V / 6Zh10B-V HF pentode tube
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