Logic circuit employing bipolar-transistors and stable upon starting-up of power supply therefor.

摘要

A logic circuit employing bipolar-transistors and including a level-shift circuit unit, in addition to a normal bipolar logic circuit, for improving a stability of the circuit upon start-up of a power supply. The logic circuit includes: an input circuit (l) receiving at least one input signal (SIN) and connected to a terminal of a power supply; a first internal circuit including a first bipolar transistor (T3), a base of which is connected to an output of the input circuit, and a level-shift circuit (D2) connected between a terminal of the first bipolar transistor and another terminal of the power supply; a level-shift circuit unit (3) connected between the terminal of the power supply and another terminal of the first bipolar transistor; a second internal circuit including a second bipolar transistor (T4) a base of which is connected to a commonly-connected point of the level-shift circuit unit and another terminal of the first bipolar transistor; and an output circuit means including a third bipolar transistor (T5) a base of which is connected to an output terminal of the second bipolar transistor, a terminal of which is connected to another terminal of the power supply and another terminal of which is provided for connection to a load circuit. A forward voltage of the level-shift circuit unit, the second internal circuit and the output circuit is higher than a forward voltage of the first internal circuit. The first to third bipolar transistors have the same operational polarities.