| 摘要 |
PROBLEM TO BE SOLVED: To improve precision of a detection output of an output detecting circuit which is used for a radio communication system performing feedback control by detecting the output power of the high-frequency power amplifying circuit and amplifies and outputs the difference between a reference voltage and the detection output. SOLUTION: The high-frequency power amplifying circuit is provided with an output power detecting circuit (220) including a detecting circuit (221) which detects an AC signal extracted from the output of the high-frequency power amplifying circuit, a bias generating circuit (222) which generates a voltage imparting an operation point of the detecting circuit, and a subtracting circuit (225) which outputs a voltage proportional to the difference between the output of the detecting circuit and the voltage generated by the bias generating circuit, and a cascade connection of two inverting amplifiers (261, 262) is used as the subtracting circuit. Further, the high-frequency power amplifying circuit is provided with an inverting amplifier (264) for feedback which inputs the output of the trailing-stage inverting amplifier and a specified voltage and supplies their difference voltage as a reference voltage to the precedent-stage inverting amplifier and on the output side of the inverting amplifier, an ON/OFF switch (SW0) and a capacity element (C0) capable of holding the output of the inverting amplifier are provided. COPYRIGHT: (C)2006,JPO&NCIPI
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