Patent ID: 7199652

Claim:
A power amplifier for amplifying a high-frequency signal and outputting an amplified signal, the power amplifier comprising: an amplification element which is a bipolar transistor or a field-effect transistor; a variable inductor connected between a base and a collector of the amplification element, or between a gate and a drain of the amplification element; and a control section for setting an inductance of the variable inductor in accordance with a change occurring in a voltage between the base and the collector of the amplification element, or between the gate and the drain of the amplification element, in a level of an amplitude modulation signal, or in a level of an envelope signal, wherein the inductance of the variable inductor is set by the control section so as to cause a parallel resonance to occur between the variable inductor, a parasitic capacitor of the amplification element, and an intrinsic capacitor of the amplification element, and wherein the intrinsic capacitor is a base-collector capacitance of the amplification element or a gate-drain capacitance of the amplification element.