Thyristor fired by overvoltage

摘要

A thyristor having an auxiliary cathode emitter region disposed in the central portion of the device in PN junction relationship with a cathode base region is disclosed. An extra impurity region of the same conductivity type as the cathode base region is disposed in the cathode base region in the central portion of the device inwardly of the outer boundary of the auxiliary cathode emitter. The extra impurity region has a higher impurity density gradient adjacent the common PN junction formed by the cathode and anode base regions than the remainder of such junction.