PURPOSE: To suppress fluctuation such as an overshoot by a method wherein external power-supply systems of a reference-voltage generation circuit and an internal power- supply circuit are separated mutually at one side of the high-level side or the low-level side or on both sides.

CONSTITUTION: An internal power-supply voltage Vint which is output from an internal power-supply voltage circuit 7 makes a charge or discharge current flow according to the operation of an internal circuit 3 and in input/output circuit 4. Thereby, a power-supply current of the circuit 7 is charged. This charge forms a potential difference by a resistance component or the like contained in an external power-supply system 11 of the circuit 7. At this time, an external power supply Vdd2 is supplied to a reference-voltage generation circuit 6 from a system 12 separated from the circuit 7; an electric current flowing in itself is stationary and comparatively small and does not cause a substantial change in the electric current. Thereby, since a reference voltage Vref output from the circuit 6 is kept constant, the circuit 7 controls the operating point of the circuit in such a way that the Vref and the Vint have a constant ratio and makes the voltage Vint constant. Thereby, it is possible to prevent a malfunction of the circuits 3, 4, and the operation speed can be made high.