| 摘要 |
PROBLEM TO BE SOLVED: To provide an analog multiple-stage amplifying circuit for improving an S/N ratio of output signal by maintaining a total gain of each amplifier to be a constant value under automatic control of a gain of multiple analog amplifiers in accordance with an input signal level. SOLUTION: The analog multiple-stage amplifying circuit comprises an input amplifier 11 to which an input signal Vin is input, an output amplifier 12 for outputting an output signal Vout, and a filter 13 provided between the input amplifier and the output amplifier in view of outputting the output signal to the output amplifier through reduction of noise element included in the output signal from the input amplifier. This analog multiple-stage amplifying circuit further comprises an automatic gain control circuit 14 for outputting a control signal to control a gain of the input amplifier to provide maximum output signal level based on the output signal from the input amplifier and a first gain adjusting circuit 15 for adjusting a gain of the output amplifier to provide a constant total gain of the input amplifier and output amplifier on the basis of the control signal of the automatic gain control circuit. COPYRIGHT: (C)2007,JPO&INPIT
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