| 摘要 |
PURPOSE:To operate suitably with simple circuit constitution by introducing the detecting voltage of a detecting device in a car-mounted or portable mobile radio set etc., feeding back a gain control signal to a high frequency amplifier and arranging a gain control amplifier to decrease or increase the amplifying degree of said high frequency amplifier in accordance with the level of the detecting voltage. CONSTITUTION:The characteristic of a gain control amplifier 13 is set and adjusted by a control adjusting resistance 13a beforehand so that the characteristic can increase almost in proportion to the output step. Thus, the output voltage in accordance with the level of the detecting voltage is negatively fed back from the gain control amplifier 13 to a high frequency amplifier 3 as a gain control voltage. For this reason, controlling is executed so that the larger the detecting voltage from a detecting device 4 is, namely, the larger the detecting output of a linking device 2 is, the smaller the amplifying degree of the high frequency amplifier 3 is. The controlling is executed so that the smaller the detecting voltage from the detecting device 4 is, namely, the smaller the detecting output of the linking device 2 is, the larger the amplifying degree of the high frequency amplifier 3 is. As the result, the detecting voltage outputted from the detecting device 4 is compressed as shown in a characteristic curve of the figure (a). |
