page_title: Pentode
section_title: Usage
hierarchical_section_title: Pentode / Usage
caption_attribution_description: English: Description: 12AE10, a Compactron dual pentode vacuum tube Source: Image by John Rehwinkel. Permission: Released into public domain by John Rehwinkel. Confirmation e-mail received from Mr. Rehwinkel has been sent by Lupo to permissions AT wikimedia DOT org. Note that Mr. Rehwinkel has also released his original, full-scale image into the public domain. Lupo 20:07, 22 February 2006 (UTC) Comment: Note that the tube is vertical, although it doesn't look that way. The left border of the glass and the vertical structures in the interior are vertical; the right boundary of the glass isn't: vacuum tubes are not perfect cylinders! History: originally uploaded as a thumbnail to the en: Wikipedia by User:EricBarbour. Larger version produced by Lupo from Mr. Rehwinkel's originals by rotating, cropping, and correcting some turquoise and white blotches.
context_page_description: A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid amplifying vacuum tube, which was invented by Gilles Holst and 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. The pentode 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.
context_section_description: Pentode tubes were first used in consumer-type radio receivers. A well-known pentode type, the EF50, was designed before the start of World War II, and was extensively used in radar sets and other military electronic equipment. The pentode contributed to the electronic preponderance of the Allies.
  The Colossus computer and the Manchester Baby used large numbers of EF36 pentode tubes. Later on, the 7AK7 tube was expressly developed for use in computer equipment.
  After World War II, pentodes were widely used in TV receivers, particularly the successor to the EF50, the EF80. Vacuum tubes were replaced by transistors during the 1960s. However, they continue to be used in certain applications, including high-power radio transmitters and (because of their well-known valve sound) in high-end and professional audio applications, microphone preamplifiers and electric guitar amplifiers. Large stockpiles in countries of the former Soviet Union have provided a continuing supply of such devices, some designed for other purposes but adapted to audio use, such as the GU-50 transmitter tube.
caption: A General Electric 12AE10 double pentode
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