| 摘要 |
A semiconductor switching circuit comprising a semiconductor element having an equivalent four-layer structure of a PNPN conductivity type formed by connecting the collector and the base of an NPN transistor respectively with the base and the collector of a PNP transistor and having a function of self-holding alternately two states, i.e. its on state and off state, a gate-turnoff thyristor, and a gate control circuit which provides to the gate of the gate-turnoff thyristor a current for turning on the gate-turnoff thyristor when the semiconductor element is conductive, and a current for turning off the gate-turnoff thyristor when the semiconductor element is cut off, whereby electrical switching is achieved by turning on and off the gate-turnoff thyristor in accordance with the state of the semiconductor element. The semiconductor switching circuit is useful as a cutoff switch used in a telephone exchange equipment since it consumes very small power because the semiconductor element is cut off when the gate-turnoff thyristor is conductive and since it has a large current capacity when the gate-turnoff thyristor is conductive.
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