PURPOSE: To prevent an off-setting due to a floating capacity from generating by discharging or charging only the prescribed quantity of the charge of the floating capacity at the section which does not execute the integrating action.

CONSTITUTION: A floating capacity Cs due to forming an input capacitor 11 as an integrated circuit is inserted into the connecting side between the input capacitor 11 and a switch circuit 2. A floating capacity Cs' due to forming an integrating capacitor 12 as the integrating circuit is inserted into the connecting side between the integrating capacitor 12 and a switch circuit 13. By providing respective switch circuits 4 and 14 to turn on at the section which does not execute the integrating action in parallel to floating capacities Cs and Cs', the charge of the floating capacities Cs and Cs' at the integrating action of the preceding section is discharged to the section which does not execute the integrating action, or charged up to a constant value.