vacuum tube (VT, electron tube or valve)
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Also see cathode ray tube ( CRT ), the specialized kind of vacuum tube that
is in most desktop display monitors.
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| What is vacuum tube ? |
A vacuum tube (also called a VT, electron tube or, in the UK, a valve ) is a
device sometimes used to amplify electronic signals. In most applications, the
vacuum tube is obsolete, having been replaced decades ago by the bipolar
transistor and, more recently, by the field-effect transistor . However, tubes
are still used in some high-power amplifiers, especially at microwave radio
frequencies and in some hi-fi audio systems.
Tubes operate at higher voltages than transistors. A typical transistorized
amplifier needs 6 to 12 volts to function; an equivalent tube type amplifier
needs 200 to 400 volts. At the highest power levels, some tube circuits have
power supplies delivering several kilovolts.
Vacuum tubes are making a comeback among audiophiles who insist that tubes
deliver better audio quality than transistors. These old-fashioned components
are more electrically rugged than their solid-state counterparts; a tube can
often withstand temporary overload conditions and power-line transients that
would instantly destroy a transistor.
The major disadvantages of tubes include the fact that they require bulky
power supplies, and the high voltages can present an electric shock hazard.
