Vacuum tube

In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify, or otherwise modify, a signal. Once used in most electronic devices, vacuum tubes are now used only in specialized applications. For most purposes, the vacuum tube has been replaced by the much smaller and less expensive transistor, either as a discrete device or in an integrated circuit. At the start of the 21st century there has been renewed interest in the vacuum tube, this time in the form of the Field-emitter microtube.

Other vacuum tube devices

A vast array of devices were built during the 1920-1960 period using vacuum-tube techniques. Most such tubes were rendered obsolete by semiconductors. Vacuum-tube electronic devices still in common use include the magnetron, klystron, photomultiplier and cathode ray tube. The magnetron is the type of tube used in all microwave ovens. In spite of the advancing state of the art in power semiconductor technology, the vacuum tube still has reliability and cost advantages for high-frequency RF power generation. Photomultipliers are still the most sensitive detectors of light. Many televisions, oscilloscopes and computer monitors still use cathode ray tubes, though flat panel displays are becoming more popular as prices drop.

Related Topics:
Magnetron - Klystron - Photomultiplier - Cathode ray tube - Microwave oven - Television - Oscilloscope - Flat panel display

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The fluorescent displays commonly used on VCRs and automotive dashboards are actually vacuum tubes, using phosphor-coated anodes to form the display characters, and a heated filamentary cathode as an electron source. These devices are properly called "VFDs", or Vacuum-Fluorescent Displays.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Some tubes, like magnetrons, travelling wave tubes, and klystrons, combine magnetic and electrostatic effects. These are efficient (usually narrow-band) RF producers and still find use in radar, microwave ovens and industrial heating.

Related Topics:
Magnetron - Travelling wave tube - Klystron - Radar - Microwave oven

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Gyrotrons or vacuum masers, used to generate high power millimetre band waves, are magnetic vacuum tubes in which a small relativistic effect, due to the high voltage, is used for bunching the electrons.

Related Topics:
Gyrotron - Relativistic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Free electron lasers, used to generate high power coherent light and perhaps even X rays, are highly relativistic vacuum tubes driven by high energy particle accelerators.

Related Topics:
Free electron laser - X ray

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Particle accelerators can be considered vacuum tubes that work backward, the electric fields driving the electrons, or other changed particles. (Like ordinary vacuum tubes many of their names end in "tron".) In this respect, a cathode ray tube is a particle accelerator.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is generically called an electron tube.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~