Within a switching network of the type wherein at least one GTO device is rendered conductive or non-conductive to control the flow of current through a load, current is drawn from the gate of the GTO device and a shunt path is connected across the main conduction path of the GTO device simultaneously in response to a turn-off signal.
A semiconductor switch has a disconnectible thyristor, a first switching transistor connected to a lead of the thyristor and a turn-off current path which emits a control electrode of the thyristor to a terminal of the lead. Given such semiconductor switches, the critical voltage rise rate dU/dt is increased for an inhibit voltage up to which an undesired ignition of the thyristor is reliably avoided. This is achieved by providing a second switching transistor having its switching path connected in the turn-off current path. Both switching transistors are conductive in the inhibiting condition of the thyristor and form a stabilizing emitter-base short.
A current switch circuit for operating with low supply voltages while not compromising dynamic range has been provided. The current switch circuit includes a differential pair of transistors having first (12) and second (20) transistors. The base of the first transistor is coupled to a bias voltage (V.sub.B) while its collector is coupled to an output (14) of the current switch circuit. The collector of the second transistor is coupled to a first supply voltage terminal while the base of the second transistor is coupled to a variable bias circuit (22) for alternately swinging the voltage applied to the base of the second transistor above or below the bias voltage applied to the base of the first transistor. When the voltage applied to the base of the second transistor is greater than the bias voltage applied to the base of the first transistor, a predetermined current is sunk from the output of the current switch. Otherwise, substantially zero current flows at the output of the current switch.
