PURPOSE: To reduce energy consumption due to battery saving by closing an analog switch and short-circuiting the output terminal and inverting input terminal of an operational amplifier when it is detected by a clock detector that a driving clock is interrupted.

CONSTITUTION: An analog switch 18 and a clock detector 19 are added. Namely, the presence and absence of a driving clock 1 or 2 of a switched capacitor is decided by the clock detector 19 and when there is no driving clock, the analog switch 18 is closed. Accordingly, for an operational amplifier 15, there is no difference in the bias of a differential pair transistor and the increase of an output off-set due to the unbalanced fluctuation of a transistor threshold VT is not generated. Thus, even when a power source is added to an LSI, the driving clock can be stopped.