| 摘要 |
PURPOSE:To quicken the leading of an AGC voltage by inserting a diode between an output of an amplifier outputting a gain control voltage and a capacitor for a filter so as to charge the filter capacitor via said diode. CONSTITUTION:An output of an amplitude detector 8 enters an automatic gain adjusting amplifier 12 and is extracted as a control voltage of a mixer and an intermediate amplifier (not shown in a figure). A parallel circuit comprising a resistor 18 and a diode 22 is inserted between an output terminal 14 of the gain adjusting amplifier 12 and the filter capacitor 16, and when a potential at the terminal 14 is higher than the potential at a terminal 20 in excess of a forward voltage drop of the diode 22, since the capacitor 16 is charged rapidly via the diode 22, the charging speed is quickened and the leading speed of the AGC voltage is improved.
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