| 摘要 |
PROBLEM TO BE SOLVED: To provide an AGC circuit which fixes a gain so that an amplitude of an input signal becomes a required amplitude. SOLUTION: The AGC circuit comprises: a variable gain amplifier circuit in which a gain to be set is variable and which amplifies an input signal with the gain; a detection circuit which detects an output signal amplified by the variable gain amplifier circuit; an error amplifier circuit which outputs an error voltage corresponding to a differential voltage between a detection voltage indicating an amplitude of the output signal detected by the detection circuit and a reference voltage for fixing the amplitude of the output signal to a predetermined magnitude; a capacitor which performs charging in accordance with the error voltage and holds a setting voltage for fixing, at a fixed value, the gain of the variable gain amplifier circuit to be applied to a gain setting input of the variable gain amplifier circuit; and a charging switch circuit which is closed for permitting the charging operation of the capacitor until the charging voltage of the capacitor becomes the setting voltage, and which is opened for prohibiting the charging operation of the capacitor after the charging voltage of the capacitor becomes the setting voltage. COPYRIGHT: (C)2007,JPO&INPIT
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