PURPOSE: To prevent a malfunction due to an undershoot at an output terminal by providing two NPN transistors(TRs) and a constant current source in an IC.

CONSTITUTION: When an output Vout of a push-pull circuit changes from a high level to a low level, an undershoot in which a voltage swings to negative side only at the moment may take place because of an L component of wiring at an output terminal 7. Thus, a parasitic TR is caused in a semiconductor integrated circuit and the circuit may malfunction. When a TR 1 is turned off and a TR 2 is turned on and an output terminal 7 goes to a low level, a TR 3 is turned on by a constant current source 9 and a TR 4. In this case, a voltage Vout at the output terminal 7 is expressed as Vout=VBE4-VBE3 (VBE4 is a base-emitter forward voltage of the TR 4 and VBE3 is a base- emitter forward voltage of the TR 3). Since the relation of VBE3=VBE0.7V is in existence, the voltage Vout is 0V and is not decreased more. Thus, malfunction due to undershoot at the output terminal 7 is prevented.