Patent ID: 7342454

Claim:
An analog multistage amplification circuit comprising: an input stage amplifier for receiving an input signal and generating a first output signal; a filter, connected to the input stage amplifier, for attenuating a noise component contained in the first output signal and generating a filtered first signal; an output stage amplifier, connected to the filter, for receiving the filtered first output signal and generating a second output signal; an auto gain control circuit, connected to the input stage amplifier, for generating a control signal for controlling gain of the input stage amplifier based on the first output signal of the input stage amplifier so that the first output signal has a maximum level; and a first gain adjustment circuit, connected to the output stage amplifier and the auto gain control circuit, for generating an adjustment signal for adjusting the gain of the output stage amplifier so that the total gain of the input stage amplifier and the output stage amplifier is kept constant in accordance with the control signal of the auto gain control circuit.