A thermionic tube having three electrodes.
Three-electrode thermionic tube containing an anode and a cathode (as does a diode) with an additional negatively biased control grid. Small variations in voltage on the grid bias result in large variations in the current. The triode was commonly used in amplifiers until largely superseded by the transistor. The tube was invented by the US radio engineer Lee De Forest.
(Électricité) Tube ŕ trois électrodes.