Innova Enterprises Khadakwasla, Pune, Maharashtra

A thyristor is a four-layer semiconductor device, consisting of alternating P type and N type materials (PNPN). The four layers act as bistable switches. As long as the voltage across the device has not reversed (that is, they are forward biased), thyristors continue to conduct electric current.

A thyristor is one of the several controllable semi conductor devices that can act either like a switch, rectifier or as a voltage regulator. The thyristor is a solid-state analogue of the thyratron vacuum tube. The name ‘thyristor’ is a combination of two words – the thyratron and the transistor. A thyristor functions a little like a transistor. It consists of three electrodes: the gate, the anode and the cathode. The gate acts as the controlling electrode. When a small current flows into the gate, it allows a larger current to flow from the anode to the cathode. A thyristor can be switched from a blocking state (high voltage, low current) to a conducting state (low voltage, high current) by a suitable gate pulse. Forward conduction is blocked until an external positive pulse is applied to the gate terminal. A thyristor cannot be turned off from the gate.