T835-8G STMicroelectronics NV

A thyristor is a solid-state semiconductor device that functions as a robust and switchable diode, allowing current to flow in one direction but not the other, often controlled by a gate electrode. It is commonly used in high-power applications such as inverters and radar generators, and typically consists of four layers of alternating P- and N-type materials. Acting as a bistable switch, there are two designs with differing methods for triggering the conducting state. In a three-lead thyristor, a small current on the gate lead controls the larger current on the anode-to-cathode path, while in a two-lead thyristor, conduction starts when the potential difference between the anode and cathode reaches a certain level (breakdown voltage). The thyristor will continue conducting until the voltage is reversed, removed, or controlled by a gate signal. Some sources use "silicon-controlled rectifier" (SCR) and "thyristor" interchangeably, while others define thyristors as more complex devices with four layers of alternating N-type and P-type substrates. Thyristors were first introduced commercially in 1956 and are widely used in controlling electric power, from light dimmers and electric motor speed control to high-voltage direct-current power transmission. They are utilized in power-switching circuits, relay-replacement circuits, inverter circuits, oscillator circuits, level-detector circuits, chopper circuits, light-dimming circuits, low-cost timer circuits, logic circuits, speed-control circuits, phase-control circuits, and more. Originally, thyristors could only be turned off through current reversal, making them challenging for direct current applications, but newer types can be switched on and off using a control gate signal, known as a gate turn-off thyristor or GTO thyristor. Unlike transistors, thyristors have a binary switching characteristic, being either fully on or off, which makes them unsuitable for analog amplification but suitable for switching purposes.