Power amplifying semiconductor integrated circuit device for use in communication equipment

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.