| 摘要 |
PROBLEM TO BE SOLVED: To provide an output power control technique capable of reducing leakage of a signal to a reception band in a high frequency power amplification circuit which fixes a bias voltage applied to a control terminal of an amplification element and varies an operation voltage (source voltage) in accordance with a signal indicating an output level, to control an output power. SOLUTION: In high frequency power amplifiers (210 and 220) including an operation voltage control circuit (220) which varies an operation voltage (Vldo) supplied to amplification elements (211 to 213) in accordance with a signal (Vramp) indicating the output level, to control the output power, a bipolar transistor is used as a transistor (Q0) for power control which outputs the operation voltage to be supplied to amplification elements. Furthermore, a clamp circuit (222) is provided which clamps an output voltage of the transistor for power control so that the transistor doesn't enter the saturation region even in the case that the signal indicating the output level is set to a maximum level within its variable range. COPYRIGHT: (C)2007,JPO&INPIT
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