Patent ID: 7271662
Filing Date: 2007-09-18
Classification: H03F,H03G

Abstract:
1. A semiconductor integrated circuit for high frequency power amplifier comprising: a power amplifier circuit including two or more transistors for amplification connected in cascade to amplify a high frequency signal to be transmit; a detection circuit which detects an input signal to a last-stage transistor of the power amplifier circuit, generates a voltage corresponding to the amplitude of the input signal, and supplies the voltage to a control terminal of the last-stage transistor; and a bias circuit which generates bias voltages to set desired idle currents to flow through the transistors for amplification respectively, wherein the last-stage transistor and elements constituting the detection circuit are formed on a same semiconductor substrate, and the detection circuit receives the bias voltage which is given to the last-stage transistor and an AC component of the input signal, generates a voltage corresponding to the level of the bias voltage and the AC signal level, and supplies the voltage to the control terminal of the last-stage transistor.