PURPOSE: To improve the operation of noise attenuation circuit by offsetting the lack of preciseness, due to the absolute value change of resistance value to occur in the process at the time of integration with the relative ratio of absolute change rate. CONSTITUTION: The voltage of input signal from an input terminal 17 is distributed by a voltage-distributing means 44, and a voltage XVi appears at an input terminal 23 of voltage/current converting circuit 19. Further, an output terminal voltage Vs' of differential amplifier is fed back into an input terminal 24 of circuit 19, and a current I1 to flow through a capacitor 22 is expressed by SC(Vs')-Vi. Also, a voltage between output terminals 28 and 29 of circuit 19 is expressed by XVi+Vs'. The transmission function of a high-pass filter circuit is expressed by a formula I. In this formula, gm represents the mutual conductance between the circuit 19 and a common emitter transistor pair 21. An output voltage Vs of a voltage buffer 43 is shown by Vi×T(s) and T(s) is the transmission function of an auxiliary signal path. Therefore, the output voltage of an operational amplifier 27 becomes an expression II, and the change portions of resistors R3 and R2 is offset by a resistor R1 so that the lack of preciseness can be improved.
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