| 摘要 |
There is disclosed a filter circuit wherein a current control portion (12) controls a constant current (I2) specifying the sum of currents flowing in transistors (T119, T120) of a control portion (11) and transistors (T19, T20) of a control portion (9) on the basis of a potential difference between an output voltage (V1) of an operational amplifier (7) and a constant voltage (V3) whereby, if there is a difference in voltage level between a control voltage (V2) of the control portion (9) and the constant voltage (V3) of the control portion (11), a filter control portion performs the same control as a reference filter output characteristic of a filter portion (8) to an ideal input-output characteristic.
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