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SCR (thyristor) latching

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Open this experiment in the circuit simulator

Objective

Trigger an SCR with a short gate pulse and see it stay on after the gate returns to zero.

Procedure

Run and compare the gate pulse with the load current.
Reduce the supply to 1 V: the SCR cannot latch.

Theory

Once the anode current exceeds the latching/holding current, the SCR stays conducting until the anode current drops below the holding current. A 1 ms pulse at t = 3 ms switches on 120 mA of load current for the rest of the run.

Questions to answer

How is a SCR turned off in a DC circuit?

Components used

2N5064 SCR, Battery / DC source, Function generator (square), Oscilloscope (2-channel), 2 × Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.