Vacuum Tube

A Vacuum Tube is a electronic device that controls electric current between electrodes in an evacuated container.

• Example(s):
  • A Fleming Valve (1904), invented by John Ambrose Fleming, was the first vacuum tube and was used as a rectifier.
  • A De Forest Audion (1906), developed by Lee De Forest, was the first triode and could amplify electrical signals.
  • A Kenotron (1915), a type of high-vacuum diode used in early radio transmitters and receivers.
  • A Tetrode (1919), an advancement on the triode with an additional grid to improve performance, was used in radio transmitters and early televisions.
  • A Pentode (1926), which added another grid to improve performance further and reduce noise, was used in audio amplifiers and radios.
  • ...
• Counter-Example(s):
  • Transistors, which replaced vacuum tubes in most applications due to their smaller size, lower power consumption, and greater reliability.
  • Diode.
  • Relay Device.
• See: Control Grid, Electric Discharge in Gases, Electric Current, Vacuum, Electrode, Voltage, Thermionic Emission, Hot Cathode, Electronics, Amplifier, Rectifier, Phototube.

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References

2024

• (Wikipedia, 2024) ⇒ https://en.wikipedia.org/wiki/Vacuum_tube Retrieved:2024-5-23.
  • A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplification and current rectification. Non-thermionic types such as a vacuum phototube, however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode (i.e. Fleming valve), was invented in 1904 by John Ambrose Fleming. It contains only a heated electron-emitting cathode and an anode. Electrons can flow in only one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grids.

    These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, television, radar, sound recording and reproduction, long-distance telephone networks, and analog and early digital computers. Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics.

    In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, cooler, and more economical than thermionic tubes. Beginning in the mid-1960s, thermionic tubes were being replaced by the transistor. However, the cathode-ray tube (CRT) remained the basis for television monitors and oscilloscopes until the early 21st century.

    Thermionic tubes are still employed in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, and high end audio amplifiers, which many audio enthusiasts prefer for their "warmer" tube sound, and amplifiers for electric musical instruments such as guitars (for desired effects, such as "overdriving" them to achieve a certain sound or tone).

    Not all electronic circuit valves / electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases, usually without a heater.

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