HIGH-FREQUENCY POWER AMPLIFIER CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a high-frequency power amplifier circuit housing a bias control circuit by which stable output power can be obtained without the change of a bias current flowing in an amplifying element, even if a power supply voltage fluctuates in a radio communication system in which the output power is controlled by changing the bias voltage of a transistor for power amplification by fixing the amplitude of an input signal. SOLUTION: The high-frequency power amplifier circuit (210) is provided with a transistor (Q17) for bias which imparts a bias by making an idle current to flow in the transistors (211-213) for power amplification with a current mirror system. The output power is controlled by changing the bias current made to flow in the transistor for bias corresponding to a bias control voltage by fixing the amplitude of the input signal in the high frequency power amplifier circuit (210). The bias control circuit (230) has the following constitution. The bias current made to flow in the transistor for bias is reduced when the power supply voltage is high. The bias current made to flow in the transistor for bias is increased when the power supply voltage is low. COPYRIGHT: (C)2005,JPO&NCIPI