Thyristor

A semiconductor switching device with three or more PN junctions. The most common type consists of four alternating layers of P-type and N-type material and has three terminals: anode (A), cathode (K), and gate (G). By applying or not applying a small gate current, it is possible to control the on/off state between the anode and cathode. It also allows switching operation by utilizing the characteristic that the device turns off when the current flowing to the anode drops below a certain value. Due to its wide range between forward average current and reverse leakage current, it can be used for high voltage and high current applications compared to transistors with the same PN junction structure. Applications include contactless switches, rectifiers, motor control, lighting brightness control, temperature control of electric heaters and furnaces, and more. TRIAC (bidirectional three-terminal thyristor) and GTO are also types of thyristors.