Patent ID: 8432227

Claim:
A power amplifier comprising: an amplifying element having a base into which input signals are input, a collector to which a collector voltage is applied, and an emitter; and a bias circuit supplying a bias current to the base of the amplifying element, wherein the bias circuit includes a bias transistor having a control terminal into which a reference voltage is input, a first terminal into which a power voltage is input, and a second terminal connected to the base of the amplifying element, a first resistor connected to the second terminal of the bias transistor, a second resistor connected between the first resistor and a grounding point, and a bias current lowering circuit which lowers the bias current when the collector voltage is lower than a first prescribed threshold value and which includes a transistor having a control terminal, a first terminal connected between the first resistor and the second resistor, and a second terminal that is grounded, and a control circuit supplying a control voltage to the control terminal of the transistor.