A semiconductor integrated circuit has an output circuit which includes a Bi-CMOS circuit of receiving an input signal, and an ECL circuit. The ECL circuit includes a differential pair for receiving an output of the Bi-CMOS circuit, na an emitter follower for receiving an output of the differentail pair. The Bi-CMOS circuit comprises a CMOS inverter connected in series between power sources; a first npn transistor, a diode, and a second npn transistor which are connected in series between the power sources; and second and third n-channel MOS transistors for turning the second npn transistor ON and OFF. This semiconductor integrated circuit provides a stable, operation and low power consumption.