PURPOSE: To detect a power source from the slow ramp like leading to the high speed leading without consuming a standby current like DC.

CONSTITUTION: At the time of a ramp like leading, a transistor MNH is put ON in a low voltage, and a N21 is made to be a high level initial state while a N22 is made to be low level initial state by the help of a transistor MP. During a slow leading, the capability increasing the N21 by the transistor MP is larger than the capability increasing the node N22 by a transistor MPH. Since the MNH is provided with a low threshold voltage, the decreasing process in the node N22 is speeded up. A capacitor CG prevents the node N22 from being charged at a high speed with the transistor MPH. When the node 21 is started in a high voltage level state, the internal voltage connected to the gate of a transistor MNI is risen, and when the MNI is turned ON, the node N21 is begun to decrease and the state of the node N22 and a PUD is inverted.