Patent ID: 7411457

Claim:
A semiconductor integrated circuit device suitable for use in mobile communication equipment, comprising a high-frequency power amplifier, said high-frequency power amplifier including: a transistor provided at a final stage of the high-frequency power amplifier, said transistor having a gate inputted with a transmit signal, a source connected with a reference potential and a drain which outputs a signal obtained by amplifying the transmit signal; a first bias circuit which supplies a bias voltage to the drain of the transistor; and a second bias circuit which supplies a bias voltage to the gate of the transistor, wherein the second bias circuit includes a gate resistor and an inductance series-connected between a bias power supply voltage and the gate of the transistor, and wherein the gate resistor has a resistance value of substantially the same order as an input impedance of the transistor at a carrier frequency thereof, which is determined by the sum of a gate capacitance of the transistor and a gate to drain capacitance thereof.