Patent ID: 6919762

Claim:
A high frequency power amplifier electric part comprising: a power amplification circuit of a multi-stage configuration in which a plurality of transistors for amplification are cascaded, which amplifies an input high frequency signal and outputs the amplified signal; a transistor for output level detection, which receives an input signal of a transistor for amplification in the final stage of the power amplification circuit; and a bias generating circuit for applying a bias to said power amplification circuit in accordance with current of the transistor for output level detection, wherein said bias generating circuit includes: a resistive element connected between an input terminal of said transistor for amplification in the final stage and an input terminal of said transistor for output level detection; a current-voltage converting means for converting current detected by said transistor for output level detection into a voltage; and an error amplifier for outputting voltage according to a potential difference between the voltage converted by the current-voltage converting means and voltage instructing an output level from the outside, a resistance value of said resistive element is set to a value so that an AC component of an input signal of said transistor for amplification can be transmitted, said transistor for output level detection passes current according to a DC component and an AC component of an input signal of said transistor for amplification in the final stage, and an output of said error amplifier is fed back to an input side of said transistor for amplification in the final stage.