PURPOSE: To provide the differential amplifier circuit which can be stably operated even under a much lower power supply voltage or can be stably operated both of under a low power supply voltage and under a high power supply voltage and can be easily manufactured.

CONSTITUTION: Differential transistors Q1 and Q2 receive constant currents I1 and I2 through an output step transistor in the single step of an upstream constant current circuit at the collectors. Thus, voltage drop is reduced rather than the conventional case. The amplified fluctuating currents of input signals A and B flow out to branch lines connected to the collectors and turn to an output signal C by a current mirror (Q11, Q12) and current mirrors (Q21, Q22) and (Q23, Q24).