PURPOSE: To process signals with high accuracy, by setting a clock duty so as to obtain an equal signal processing error between a discharge section and a charge section of a capacitor.

CONSTITUTION: Capacitors C1 and C3 flow currents and are reset in an ON section of a clock 1, and no electric charge flows to a capacitor C4. At the same time, a capacitor C2 is charged with an input V1. If the largest time constant of this action is obtained by the charging of the C2, an equation 1 is satisfied. In an ON section of a clock 2, the C1 charges the electric charge corresponding to the input V1 to capacitors C3 and C4 connected in parallel to each other via an amplifier 5. The C2 transfers the electric charge which is charged during the ON section of the clock 1 to capacitors C3 and C4 with inversion of the polarity. If the maximum time constant of this ON section is given by the charging of the C2, an equation 2 is obtained. Then the ratio between clocks T1 and T2 is set as shown by an equation 3 in order to obtain an equal error between equations 1 and 2. The clock duty is set in such a way.