PURPOSE: To monitor the load current of the collector of an NPNTR by using the NPNTR which has the emitter connected in common to the cathode terminal of the thyristor composed of a PNPTR and an NPNTR, and also has the gate terminal and base connected in common.

CONSTITUTION: A thyristor consists of an NPNTR204 whose collector connects with the base of a PNPTR202. The collector of the TR202 and the base of the TR204 are connected in common to obtain the gate terminal 201 of the thyristor. The base of an NPNTR207 is connected to the gate terminal 201. The emitter of the TR207 is connected in common. In this constitution, a sense terminal is connected to the collector 206 of the TR207, and the load current is monitored by a current flowing to the sense terminal. Consequently, a semiconductor switch which is integrated easily and has a load current monitoring function is obtained.