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High frequency power amplifier circuit and electric component for high frequency power amplifier

  • US 20060066398A1
  • Filed: 09/16/2005
  • Published: 03/30/2006
  • Est. Priority Date: 09/24/2004
  • Status: Active Grant
First Claim
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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.

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