| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of components and a circuit scale by eliminating the need of capacity for detection and sharing a detection circuit about a device having a plurality of signal systems respectively including an AGC (automatic gain control) function part. SOLUTION: A gain control amplification circuit 1 of a first signal system and a gain control amplification circuit 2 of a second signal system share the detection circuit 15. By changing switches 56 and 57, a state in which the first signal system performs an AGC operation and a state in which the second signal system performs an AGC operation are switched. The detection circuit 15 comprises a full-wave rectification circuit for rectifying an output of a gain control amplifier, a comparator for comparing an output of the full-wave rectification circuit with prescribed threshold voltage, an up/down counter for switching counting directions according to an output of the comparator and a D/A converter circuit for converting an output of the up/down counter into direct current voltage. The up/down counter sets an up count clock and a down count clock frequency independently. COPYRIGHT: (C)2006,JPO&NCIPI
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