Thyristor (SCR) - Silicon Controlled Rectifier

Type: Four-layer (PNPN), three-terminal semiconductor device

Terminals: Anode (A), Cathode (K), Gate (G)

Function: Acts as a controlled switch for high-power applications. Conducts current only after gate trigger and remains on until current drops below holding current.

Key Features:

• • Unidirectional current flow (Anode to Cathode)
• • Latching behavior – stays ON once triggered
• • High voltage and current handling capability
• • Used in AC power control (e.g., dimmers, motor controls)

Triggering Methods: Gate triggering most common; also dv/dt, temperature, or light (in LASCR).

Turn-off: Requires anode current to fall below holding current or forced commutation.

Applications: Phase control, rectifiers, surge protection, motor speed control.