Abstract: Delay time characteristics of rise time and fall times of an output in a CMOS output buffer converting CMOS logic signals into ECL logic signals are made coincident with each other to eliminate various kinds of bias-voltage power supplies required for discharging the charge of capacitance parasitically present on an output-side. The amplifier 1 amplifies an input and supplies a driving input for an outputting P-channel MOSFET 2. A bypass control circuit 4, which inputs gate signals 1001 from the amplifier 1 and a drain potential of the outputting P-channel MOSFET 2 from an output terminal 105, acts as a NAND circuit of those two inputs, and feeds gate signals 1002 so as to cause conduction of the bypassing P-channel MOSFET only at a transient period during which a "high" level outputted to the output terminal 105 is converted into a "low" level, thus the charge on a load capacitance parasitically arisen on the output terminal 105 side is discharged.