To supply a sufficient base current for a heterojunction bipolar transistor(HBT) for power amplification regardless of the variation of HBT, by connecting a resistor between the base and emitter of HBT for power amplification.

A signal inputted from a signal input terminal 1 is inputted to the base of HB 10 through a capacitor 5 and outputted from a signal output terminal 2 through a capacitor 6 from its collector. The collector current of this HBT 10 is supplied through a spiral inductor 9 from a power source terminal 4. A voltage applied from a base applying voltage terminal 3 is divided by resistors 7 and 8 to give a base bias voltage to HBT 11. HBT 11 amplifies current to supply a base current to HBT 10 from its emitter. For this HBT 11, a resistor 12 is inserted between its base and emitter.