PURPOSE: To eliminate an error caused due to the wiring capacitance by providing an operational amplifier connecting an inverted input to the 1st, 2nd and 3rd discharge switches of the 1st, 2nd and 3rd sampling capacitor.

CONSTITUTION: An input signal v1 fed to a terminal 1 is sampled by a capacitor 8 at a time (n-2)T. The signal is sampled in a capacitor 8 at a time (n-3/2)T and sampled in a capacitor 7 at a time (n-1)T. The electric charge in the capacitors 6, 8 at the time (n-1)T is transferred to the integration capacitor 9 via switches 2, 4 respectively. The signal v1 is sampled in the capacitor 8 at a time (n-1/2)T and the charge in the capacitors 7, 8 is transferred to the integration capacitor 9 at a time (nT) via the switches 3, 4 respectively. The charge in a feedback capacitor 10 is transferred to the integration capacitor 9 at times (n-1)T and nT. The operational amplifier 11 applies integration and an output signal v2 is generated at an output terminal 12.