Vakuumröhre

Vakuumröhre, also known as a vacuum tube or thermionic valve, is an electronic component that controls electric current flow in a high vacuum between two or more electrodes. These electrodes are typically enclosed in a sealed glass or metal envelope. The most basic vacuum tube is the diode, which contains a heated cathode that emits electrons and an anode that collects them. By applying a voltage between these electrodes, current can be made to flow.

More complex vacuum tubes, such as triodes, tetrodes, and pentodes, incorporate additional electrodes called grids. These grids, placed between the cathode and anode, can modulate the flow of electrons. By applying a small voltage to a grid, a larger change in current between the cathode and anode can be achieved, enabling amplification. This amplification capability was fundamental to the development of early electronic devices.

Vacuum tubes were crucial in the development of radio, television, radar, and early computers. Their ability to switch and amplify signals made them the backbone of electronics for decades. However, they suffered from several drawbacks, including their relatively large size, fragility, susceptibility to vibration, high power consumption, and limited lifespan due to filament burnout. These limitations led to their gradual replacement by smaller, more robust, and energy-efficient semiconductor devices like transistors starting in the mid-20th century. Despite their decline in mainstream applications, vacuum tubes are still used in some specialized audio equipment, high-power radio transmitters, and certain scientific instruments due to their unique sonic characteristics or high voltage handling capabilities.