Patent ID: 7688133

Claim:
A power amplifier comprising: an amplifying transistor for amplifying RF signals, having a base connected to an input terminal and a collector connected to an output terminal; a bias circuit for supplying a bias current to the base of said amplifying transistor; first and second capacitors and first and second inductors; a first diode having an anode and a cathode, the cathode being connected to the input terminal via said first capacitor; a second diode having an anode and a cathode, the anode being connected to the output terminal via said second capacitor, and connected to a first power terminal via said first inductor; a matching attenuating circuit connected between the anode of said first diode and the cathode of said second diode, for reducing impedance mismatch at the input terminal and at the output terminal, and attenuating the RF signals; a first current mirror circuit connected to the cathode of said first diode via said second inductor, for driving said first and second diodes; a serial resonant circuit connected between the base of said amplifying transistor and a grounding point, and having a resonance frequency within an operating frequency band of said amplifying transistor, and a switch connected between said serial resonant circuit and the grounding point, wherein, in an amplification mode, said bias circuit supplies the bias current to said amplifying transistor, and said first current mirror circuit turns off said first and second diodes and said switch, and in an attenuation mode, said bias circuit supplies no bias current to said amplifying transistor, and said first current mirror circuit turns on said first and second diodes and said switch.