| 摘要 |
PURPOSE:To decrease remarkably current consumption at low transmission output power by controlling directly an input bias voltage of a power amplifier being the final amplifier stage with an APC loop circuit to use a small-sized circuit for the power gain control of the power amplifier. CONSTITUTION:A transmission input signal from an input terminal 10 is amplified by a power amplifier 11 and a transmission output signal from an output terminal 2 is irradiated as a transmission wave. A part of the output of the power amplifier 11 is extracted by a directional coupler 6 and its output is converted into a current/voltage proportional to the transmission output power by a detection circuit 7 and the result is inputted to a differential amplifier 9. On the other hand, a reference voltage of a reference voltage generating circuit 8 generating a reference voltage in response to a set output by using a control signal from a control input terminal 3, compared with a DC voltage from the detection circuit 7, an error voltage is amplified and the voltage controls the input bias voltage of the power amplifier 11. In the APC loop circuit, the reference voltage set by the control signal from the control input terminal 3 is compared with the detection voltage to control a desired transmission output power.
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