Controllable space-charge-limited impedance device for integrated circuits

Claim 1

A compound circuit device including a controllable spacecharge-limited impedance element in series with a bipolar transistor comprising a body of semiconductor material comprising: a relatively high resistivity bulk portion of one type semiconductivity; a first surface zone of the other type semiconductivity providing an emitter zone for the transistor; a second surface zone of the other type semiconductivity spaced from the first zone, the second zone providing a collector zone for the transistor and simultaneously providing one of two surface zones for the impedance element; a first relatively low resistivity surface portion of the one type semiconductivity disposed between the first and second surface zones and delimited in lateral extent thereby, said first surface portion providing a base zone for the bipolar transistor; a third surface zone of the other type semiconductivity spaced from the second zone, said third zone providing the other of two surface zones for the impedance element; a second relatively low resistivity surface portion of the one type semiconductivity disposed between the second zone and the third zone and delimited in lateral extent thereby, said second surface portion providing a control zone for the impedance element; and first, second, third, fourth, and fifth electrodes providing electrical connection, respectively, to the emitter zone, to the base zone, to the collector zone, to the control zone, and to the other zone of the two surface zones for the impedance element; each of the first, second, and third surface zones defining first, second, and third PN junctions, respectively, with contiguous material of the one type semiconductivity.