SCR vs GTO thyristors

by ourcircuits

7 parts

An SCR and a gate-turn-off thyristor side by side on one 24 V, 60 Hz line, each with a 100 Ω load and a gate driver referenced to its own cathode, both receiving the same command: +5 V from 45° to 135°, then −5 V. The scope shows the family's defining split — the SCR latches at 45° and conducts to the current zero-cross at 178°, sailing straight through the gate drop-out, while the GTO obeys the −5 V and cuts off at 135°. Both are behavioural latch macromodels: trigger at gate 0.7 V above cathode while forward-biased, an ideal low-resistance on-state (the 24.0 V load peak shows no forward drop), commutation at the current zero, plus the GTO's negative-gate unlatch. Real gate sensitivity, dV/dt triggering, di/dt limits and turn-off current gain are not simulated.