Thyristor with multiple groups of insulated control electrodes

Claim 1

A thyristor, comprising: a first conductivity type emitter connected to an anode terminal; a second conductivity type first base directly adjacent to and contacting said emitter; a first conductivity type second base directly adjacent to and contacting said first base such that said first base lies between said second base and said emitter; a plurality of second conductivity type emitter zones each provided with corresponding cathode portions connected to a cathode terminal and arranged in the second base; a plurality of emitter groups being provided in respective second base regions, each emitter group being formed of a plurality of said emitter zones; a central initiating electrode contacting the second base and surrounded by said emitter groups; each emitter zone having a flanking second conductivity type region connected by a second conductivity type channel region, a conductive coating bridging a pn junction between the second base and flanking region, and a gate electrode lying on a non-conductive layer over the channel region; for each emitter group all of the gates associated therewith being commonly connected by a conductive path to a common terminal, the conductive path and common terminal being insulated from the second base; a common contact insulated from the second base and surrounding the emitter groups and associated common terminals, and said common terminals lying adjacent to but separated from the common contact; and an electrical connection running from the group common terminal of selected emitter groups to the adjacent common contact, whereby any emitter group which is determined to be non-functional need not be selected to be connected to the common contact.