| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic gain control circuit of which the gain control is accelerated and of which the production cost is reduced even when a detection value of an input signal level is dispersed. SOLUTION: An input level detecting circuit 42 detects the level of an input signal, and in accordance with the detection value, a rough control circuit 43 outputs a rough control signal that is preset for roughly controlling a gain of a variable gain amplifier circuit 41. A level detecting circuit 44 detects a level of an output signal of the variable gain amplifier circuit 41 and in accordance with the detection value, a fine control circuit 45 outputs a predetermined fine control signal for a fine control of the gain of the variable gain amplifier circuit 41. An adder circuit 46 adds the rough control signal and the fine control signal to generate an added control signal. A control circuit 47 detects a level difference between the added control signal and the rough control signal and when the level difference is a predetermined value or more, a value of the rough control signal preset to the rough control circuit 43 is updated into a value of the added control signal. COPYRIGHT: (C)2004,JPO&NCIPI
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