A through-current Ic of a comparator circuit is switched in accordance with a response speed required with respect to a current consumption. Additionally, a through-current Is of a shifter circuit, which sends to the comparator circuit an output signal at an appropriate level transmitting a difference between an internal power supply potential Vdd and a reference potential Vref is switched according to the required response speed. When a device is in a standby state requiring a small current consumption in internal power supply potential Vdd, both through-currents Ic and Is are set small so that the whole current consumption can be further reduced.