| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter circuit and a semiconductor integrated device both having a stable frequency characteristic. SOLUTION: The filter circuit 10 is provided with: a first gm amplifier 11; a first capacitor C1 connected between the output terminal of the first gm amplifier 11 and a signal input terminal 14; a second capacitor C2 separably parallel-connected to the first capacitor C1; a buffer amplifier 16 for performing feedback control so that a potential difference between both the ends of the second capacitor C2 becomes zero when the second capacitor C2 is separated from the first capacitor C1; a second gm amplifier 12 connecting one input terminal to the output terminal of the first gm amplifier 11; a third capacitor C3 connected between the output terminal of the second gm amplifier 12 and a ground terminal 18; a fourth capacitor C4 separably parallel-connected to the third capacitor C3; and a buffer amplifier 13 for performing feedback control so that a potential difference between both the ends of the third capacitor C3 becomes zero when the fourth capacitor C4 is separated from the third capacitor C3. COPYRIGHT: (C)2008,JPO&INPIT
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