Patent ID: 8008974

Claim:
A power amplifier system, comprising: a power amplifier for receiving a bias voltage and a bias current from a power voltage source and having a gain controlled according to the magnitude of the bias voltage and the bias current; a voltage detection controller for detecting the magnitude of the bias voltage being supplied to the power amplifier and for comparing the magnitude of the bias voltage with a predetermined reference voltage to control the magnitude of the bias voltage; and a current detection controller for detecting a voltage having a magnitude equivalent to the magnitude of the bias current being supplied to the power amplifier and for comparing the magnitude of the voltage equivalent to the magnitude of the bias current with the predetermined reference voltage to control the magnitude of the bias current, wherein the voltage detection controller comprises: a first comparator having: one input terminal for receiving the reference voltage; another input terminal connected to a bias voltage input terminal of the power amplifier for receiving the bias voltage; and an output terminal for outputting a result of comparing the reference voltage with the magnitude of the bias voltage; and a first transistor having: a source connectable to the power voltage source; a drain connected to the bias voltage input terminal of the power amplifier; and a gate connected to the output terminal of the first comparator.