| 摘要 |
PROBLEM TO BE SOLVED: To solve problems that in an electric signal amplifier employing an operational amplifier in which feedback path is arranged with a capacitor, a flat gain frequency characteristic cannot be obtained and a phase margin gets smaller because a peak appears at a change in the gain with respect to the frequency when a voltage follower is used to match DC levels at an output terminal and an input terminal of the operational amplifier. SOLUTION: An input signal is input to a terminal Vin+ of the operational amplifier 20, a terminal Vin- is connected to ground via a capacitor 24, and a capacitor 26 is arranged in the feedback path formed between the terminal Vin- and the output terminal Vout. Through the configuration above, a resistance circuit 28 is connected between the terminals Vin- and Vout. The resistance circuit 28 is configured to include a MOSFET 30 and a gate voltage generating circuit 32, and a gate voltage for bringing the MOSFET 30 to have a sub-threshold characteristic is applied to the gate voltage generation circuit 32. Thus, the channel of the MOSFET 30 obtains a high resistance. COPYRIGHT: (C)2006,JPO&NCIPI
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