Patent ID: 7123094

Claim:
A high frequency power amplifier circuit, comprising: a plurality of amplifying stages which are coupled in cascade between an input terminal and an output terminal for amplification, each of the amplifying stage including a field effect transistor as an amplifier; a bias circuit which supplies bias voltages set to predetermined values to control terminals of the plurality of amplifying stages; and a power source voltage control circuit which is coupled between a power source voltage and the amplifying stages, receives the power source voltage, and generates a first power voltage for a final one of said amplifying stages, said final amplifying stage being nearest to the output terminal and generates a second power voltage for preceding ones of said amplifying stages in accordance with an output power specification signal, wherein the power source voltage control circuit includes a first control transistor for controlling the first power voltage and a second control transistor which is different form the first control transistor for controlling the second power voltage, and wherein the power source voltage control circuit set the second power voltage to determine a current flow on said preceding amplifying stages in a saturate state, when the first power voltage is set to determine a current flow on the final stage in a linear state.