Thyristor Devices designed specifically for high-power switching application. Constructed of 4 semiconductor layer (pnpn layer). pnpn layer can be represented as a pnp transistor and an npn transistor.
Thyristor It is a device that acts as a latch. It use internal feedback to produce switching actions used for over voltage protection, motor controls, heaters, lighting systems, and other heavy-current loads. Other names: Shockley diode; 4-layer diode; PNPN diode; Silicon Unilateral Switch (SUS).
History of Thyristors Early 1900s: vacuum tube ` – Lee DeForest --- triode, 1906 1920-1940: mercury arc tubes to convert 50Hz, 2000V to 3000VDC for railway 1930s: selenium rectifiers 1948 - Silicon Transistor, (BJT) introduced (Bell Labs)