Common emitter amplifiers operating from a multiplicity of power supplies

Abstract

A technique for operating a common emitter circuit from a plurality of supply voltages. In one embodiment, a current mirror includes a plurality of diode-connected transistors each connected between a source of current and associated supply voltages. Corresponding current mirrors are each connected between an output terminal associated supply voltage leads, thereby providing an output current mirrored from the soure of current, regardless of which of the supply voltages are activated, and regardless of their particular levels. In another embodiment, a regulator includes an output transistor having a plurality of current handling terminals, each connected to an associated supply voltage, and a second current handling terminal coupled to an output terminal. Feedback is provided between the output and the control terminal of the output transistors, insuring a regulated output regardless of which of the supply voltages are active at any given time, and without regard to the specific levels of the plurality of supply voltages. The feedback is provided by a differential input amplifier, or the like, and can derive its supply voltage from a plurality of supply leads utilizing a diode OR connection in order to insure that suitable feedback supply is provided regardless of the levels of the various supply voltages. In another embodiemnt, an operational amplifier circuit includes pull up and pull down output transistors, having their collectors connected to the output terminal, and one of a plurality of emitters connected to one of a plurality of positive supply voltages and negative supply voltages, respectively.