In order to reduce noise in a controlling circuit including digital circuitry and analog circuitry constructed together on a single CMOS integrated circuit, a regulator is constructed as part of the integrated circuit. A power supply is directly connected to the digital circuitry, and a voltage output of the regulator is supplied to the analog circuitry. The output state of the regulator may be controlled by a switch. Degradation of the performance characteristics of the analog circuitry while the digital circuitry is being operated can be prevented by electrically isolating the power supply to the digital circuitry from the power supply to the analog circuitry. Since the regulator is built into the integrated circuit, the number of externally provided components is thereby reduced, further contributing to the downsizing of an electronic device such as a camera. Furthermore, even when the power supply of the digital circuitry fluctuates greatly, the effects on the analog circuitry are minimized.