All-npn transistor driver and logic circuit

Abstract

An all-NPN bipolar transistor driver circuit characterized by low standby power dissipation and fast response, particularly at high input driving conditions. The bases of a pair of NPN transistors are commonly connected to an input terminal. The emitter of a third NPN transistor is connected to the collector of one transistor of the transistor pair and to an output terminal. The collector of the other transistor of the transistor pair is connected to the base of the third NPN transistor. The base and collector of the third NPN transistor are coupled to a first biasing means. The emitters of the transistor pair are connected to a second biasing means through respective resistors so that those emitters may be independently biased. The values of the biasing means are set, relative to the lowest input voltage excursion occurring at the input terminal so that no current flows through transistor pair during the lowest input voltage excursion. Various circuit extensions, based on the above driver circuit, are also described to provide logic functions represented by output logic signals which are in-phase as well as out-of-phase relative to the applied input logic signals.