Patent ID: 7276778

Claim:
A semiconductor system, comprising: an insulating gate bipolar transistor including a well region of a second conductivity-type selectively disposed on a surface layer of a semiconductor substrate, the substrate of a first conductivity-type; an emitter region of the first conductivity-type, selectively disposed on a surface layer in the well region; an insulating film that partially covers the well region and the emitter region; a control electrode extending through the insulating film; a first well electrode electrically connected to the well region; an emitter electrode electrically connected to the emitter region; a well layer of the second conductivity-type disposed on a back surface side of the substrate; and a second well electrode electrically connected to the well layer; a first terminal; a self arc-extinguishing device connected between the emitter electrode and the first terminal; a rectifying device connected between the first well electrode and the first terminal; and a second terminal connected to the second well electrode; wherein the insulating gate bipolar transistor, when a current that flows between the first and second terminals is small, operates as a thyristor, and when the current is large, operates as a bipolar transistor, and wherein the insulating gate bipolar transistor automatically switches between a state in which it operates as a thyristor and a state in which it operates as a bipolar transistor, based on the current.