PURPOSE: To shorten the delay time for state change, by providing a diode, which discharges electric charge stored in bases, between bases of signal input and output- stage transistors, in a semiconductor logical circuit using bipolar transistors.

CONSTITUTION: When the base voltage of an input-stage transistor T1 becomes equal to or larger than the sum of a Vf (forward voltage) of a buffer-stage transistor T2 and an output-stage transistor T4 and the forward voltage between the base and the collector of the input-stage transistor T1, a low-potential signal is outputted to the output. When the input signal changes from a low potential to a high potential, transistors T2 and T4 are changed to the turning-on state from the turning-off state, however, the switching speed is high, and therefore, the delay time of the gate is short. When the input signal changes from a high potential to a low potential, electric charge stored in the base of the transistor T4 is discharged through a diode D1, and the transistor T4 is turned off rapidly because the forward voltage of the diode D1 is smaller than that of the transistor T4, and the delay time of the rise of the gate becomes short.