PURPOSE: To reduce the delay time and the power consumption by providing the 2nd and 3rd transistors (TRs) constituting a current mirror to a load of the 1st TR of emitter follower constitution and connecting the 1st and 2nd diodes to the 2nd and 3rd TRs respectively.

CONSTITUTION: Each terminal of the 1st and 2nd diodes 7, 8 is connected in common to the load of the 1st TR 4 of emitter follower constitution and the other terminal of the 1st diode is connected to the collector, base of the 2nd TR 9 and the base of the 3rd TR 10. Further, the emitter of the 2nd and 3rd TRs is connected respectively to ground, the collector of the 3rd TR is connected to the other terminal of the 2nd diode so as to give the constitution where the common connecting point of the 1st and 2nd diodes is used as an input terminal and the collector of the 3rd TR is used as an output terminal. Thus, in selecting the Miller ratio properly and giving a minimum current only to the input terminal, the power consumption is reduced.