| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-frequency power amplifier circuit in which a sufficient detection output can be obtained, even in a region of low-level required output power, so that desired output power control can be practiced by a control loop in a radio communications system, in which output power is detected to perform feedback control. SOLUTION: There is provided an output power detecting circuit (220) for detecting an output power level, based on an alternate current signal input, via a capacitive element, from a final amplifying stage (213) of the high-frequency power amplifier circuit (210). In the output power detecting circuit (220), based on an output power control voltage (Vapc) and a voltage (Vref) for acting as a reference, a current (Isu) which depends on the output power control voltage is generated, to be supplied to the output power detection circuit, in a state where the output power control voltage is lower than a certain level. Also, the output power detection circuit is configured so that detection sensitivity is improved, according to the current. COPYRIGHT: (C)2005,JPO&NCIPI
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