Logic circuit driver stage for TTL or open collector output - pulls up voltage drop across three diodes and base-emitter of npn transistor

摘要

The driver stage includes a transistor (2) which is controlled by an input signal (1) and whose emitter is connected to a negative supply voltage (3) and whose collector forms the output (4) of the driver stage. The output is connected through a diode (5) to the emitter of a second transistor (6) whose collector is coupled to the positive supply voltage (7) and whose base is connected both to the positive supply voltage via a current source (8) and to the negative supply voltage via at least one diode (9,10,11). The emitter-collector path of a third transistor (12), controlled by the input signal, is connected between the negative supply voltage and a connection point of the diode(s) (9,10,11). ADVANTAGE - Protected against negative potential which could cause malfunction in integrated circuit.