A triode is a type of vacuum tube (or valve in British English) with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electrical amplification device.

The original three-element device was invented in 1906 by Lee De Forest who called it an Audion. The Audion did incorporate, in an imperfect form, the key principle of allowing amplification. The name triode appeared later, probably when it became necessary to distinguish it from other generic kinds of vacuum tubes with more elements (Tetrodes, Pentodes). The original Audion tubes were not vacuum tubes however, as they deliberately contained some gas at low pressure. The name triode is only applied to vacuum tubes.

Triodes are largely obsolete, having been replaced by the transistor, but do still find application where power consumption and overall size are not concerns, but low component count and high power capacity are. They are also still valued by musicians and audiophiles for amplification purposes, as some claim that triodes are still more linear at audio-frequency ranges and have less musical distortion characteristics.

See also

• Vacuum tube
• 12AX7

Vacuum tubes

Triodenröhre | Triodo | Triode | Trioda | טריודה | Triode | Trioda | Tríodo | Электровакуумный триод | ไตรโอด