PURPOSE: To enable to obtain stable reference voltage without increasing electric power consumption for variation of load by connecting an operational amlifier having connected inversion input end with an output end to the output end of a reference power source.

CONSTITUTION: As the inversion input terminal and output terminal 21 of the operational amplifier 22 are connected directly, gain of this operational amplifier 22 becomes 1, and voltage of non-inversion input appears in the output end 21. Further, as output impedance of the operational amplifier 22 is as low as less than 1, potential of the output end 21 does not change even when load of the operational amplifier 22 changes. Accordingly, by using this circuit as the reference voltage generating circuit of switched capacitor integrators 23, 24, stable reference voltage is supplied and characteristic of the integrators 23, 24 becomes stable. As stable reference voltage is obtained even if large electric current is not let flow in resistances 18, 19, it is suitable also for an integrated circuit.