High frequency power amplifier electric parts and radio telecommunication system

摘要

The present invention provides a high frequency power amplifier of a multi-stage configuration in which a plurality of transistors for power amplification are cascaded, with reduced distortion of a signal in a region where an output power level is low and improved power efficiency. In a high frequency power amplifier electric part in which a plurality of transistors for power amplification are cascaded, a transistor for output level detection is provided whose gate terminal receives a gate input of a transistor for power amplification in the final stage via a resistive element of which resistance value is 100 Omega or less. Current detected by the transistor is converted to voltage. The voltage is compared with output control voltage by an error amplifier. Voltage according to the potential difference is applied to the gate terminals of the transistors for power amplification in the amplification stages to thereby pass idle current.