Gatetriggering
Gatetriggering, or gate triggering, is the method by which a thyristor, such as an SCR or a triac, is turned on by applying a signal to its gate terminal. A gate current must reach a specified value, known as the gate trigger current I_GT, or gate trigger voltage V_GT, to initiate conduction from anode to cathode (or MT2 to MT1 in a triac). Once triggered, the device latches, maintaining current until the load current falls below its holding current I_H.
The minimum current needed to guarantee turn-on is I_GT; the current required to keep the device on
Triacs are bidirectional thyristors that use gate triggering in both positive and negative halves, whereas SCRs
Limitations of gate triggering include limited dv/dt immunity, sensitivity to temperature, and the need for gate