Abstract: A source of direct current has its opposite polarity terminals connected to an electrical load via a transistor functioning as a chopper. A reactor is provided which comprises a primary winding also connected between the DC source and the load, a secondary winding adapted to apply a biasing voltage across the base and emitter of the transistor, and a tertiary winding constituting a part of the energy release circuit through which the energy stored in the reactor during each conducting period of the transistor is released. A base control circuit in the form of, for instance, a voltage regulating diode is connected to the base of the transistor. The transistor performs the desired "chopping" or current interrupting function to permit the delivery of substantially constant DC power from the DC source to the load.

Abstract: A monocrystalline silicon wafer is prepared which has formed therein the usual emitter, base and collector regions. A groove is then formed to a predetermined depth in the top surface of the silicon wafer so as to extend along the P-N junction between the base and emitter regions. A silicon oxide layer is formed over the wafer, as by heating the same in an oxidative atmosphere, and the wafer is succeedingly heated in a hydrogenous atmosphere. The silicon oxide layer may be selectively photoetched away where the electrodes are to be formed for the emitter, base and collector of the transistor.