Thyristor

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.