Patent ID: 7616060

Claim:
A power amplifier comprising: an input terminal and an output terminal; first, second, and third capacitors; an amplifying transistor having a base connected to the input terminal via the first capacitor and a collector connected to the output terminal, and which amplifies a radio frequency signal; a bias circuit which supplies a bias current to the base of the amplifying transistor; a first diode having a cathode connected to the input terminal via the second capacitor, and an anode; a second diode having an anode connected to the output terminal via the third capacitor, and a cathode; a matching and attenuating circuit which is connected between the anode of the first diode and the cathode of the second diode, which reduces impedance mismatches on an input terminal side and an output terminal side, and which attenuates the radio frequency signal; a first inductor connected between the anode of the second diode and a power supply terminal; a second inductor; and a current mirror circuit which is connected to the cathode of the first diode via the second inductor, and which drives the first and second diodes, wherein, in an amplification mode, the bias circuit supplies a bias current to the amplifying transistors and the current mirror circuit turns off the first and second diodes, and in an attenuation mode, the bias circuit supplies no bias current to the amplifying transistor and the current mirror circuit turns on the first and second diodes.