| 摘要 |
PURPOSE:To prevent the degradation of cross modulation distortion (IMD) by increasing or reducing the power source voltage of, for example, an amplifier circuit in the output circuit driving stage of a transmitter in accordance with increase or reduction of the amplitude of an audio output to prevent suppression of a high frequency peak output subjected to amplitude modulation. CONSTITUTION:The output of a peak voltage compensating circuit 20 is supplied to a driving stage-side power supply terminal 15 of an amplifier 10. A low frequency signal for modulation is supplied to a modulating low frequency signal input terminal 21 of this peak voltage compensating circuit 20, and the voltage of the output terminal, namely, the driving stage-side power supply terminal 15 of the peak voltage compensating circuit 20 is increased or reduced in accordance with increase or reduction of the amplitude of said low frequency signal for modulation. That is, even if a large current is flowed in the output stage in proportion to increase or reduction of the amplitude of the input signal and the voltage of a power source 17 falls, a large input power is supplied to the output stage because the power source voltage of a driving stage 12 is raised, and thus, reduction of the power source voltage and reduction of the peak output power due to nonlinearity for a large input signal of a transistor in the output stage are compensated.
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