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Vacuum tube

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Structure of a vacuum tube triode
A vacuum tube, type 6P1P

A vacuum tube (also called a valve in British English) is an electronic device used in many older model radios, television sets, and amplifiers.


John Ambrose Fleming invented the first vacuum tube, the diode, in 1904. Lee De Forest created the "audion" in 1906 (which was improved by others as the triode in 1908) and used in the first telephone amplifiers.

Vacuum tubes produce a lot of heat as they have a filament like a light bulb, and being made of glass they are fragile and can break. Vacuum tubes were used in the first computers like the ENIAC, which demanded lots of maintenance because of the heat produced.

For this reason, when the transistor became cheaper in the 1960s, most manufacturers of radios, television sets, and amplifiers began using transistors instead of vacuum tubes. Transistors were also much smaller, worked on lower voltages, used much less power, were much less likely to be damaged by being dropped and had extremely long life. Eventually they were also much cheaper than glass valves.[1]

Current uses

In the 2000s, vacuum tube devices are rarely used in common electronic equipment. The cathode ray tube was used for the picture display in television receivers, though these have been replaced by non-vacuum tube types such as liquid crystal and plasma displays.

There are still a few applications that use vacuum tubes:

  • Systems which need high frequency operation, high-power output or very high amplification, such as television transmission, X-ray machines, radar, and microwave ovens.
  • People who enjoy listening to music on high-quality home stereo systems sometimes buy amplifiers which use vacuum tubes to hear their music. (See tube sound).
  • Musicians who play electric musical instruments such as electric guitar sometimes use guitar amplifiers with vacuum tubes.


  1. St. Clair Kilby, Jack (17 September, 2001). "Turning Potential into Realities: The Invention of the Integrated Circuit" (pdf). ChemPhysChem. Wiley Online Library. p. 483.;2-Y/pdf. Retrieved 2010-10-05.

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