Thread: SCR in action

When in action, SCR is like two over lapping transistors-the n-p junction of a pnp transistor overlapping the n-p junction of an npn transistor. When a trigger current is applied to the gate terminal, T1 conducts and its collector current provides bias to T2 and it also conducts. At the same time, the collector current of T2 provides more base current to Tl. This positive feedback effect ensures that both transistors are conducting. Once this condition is attained, Tl and T2 remain latched and no more gate current is required.



If the voltage between the anode and cathode rapidly increases, capacitive coupling may induce enough charge into the gate to trigger the device. This is referred to as 'dv / dt triggering.' This may not switch the SCR into full conduction rapidly and the partially triggered SCR will dissipate more power possibly harming the device.