PURPOSE: To eliminate the influence of noise even when a signal including a noise component is inputted to a set terminal, or a reset terminal, by connecting a capacitor between the collector of a transistor consisting of a current mirror circuit, and a reference potential.

CONSTITUTION: The collector current of a transistor 5 charges a capacitor 13 by inputting a voltage larger than VBE to a set input terminal 1, thereby, the terminal voltage of the capacitor 13 increases. In this way, the base voltage of a transistor 16 increases, then the transistor 16 goes to an energized state, and a transistor 18 goes to a cut off state. And the collector current of a transistor 4 flows into the base of a transistor 8, then the transistor 8 becomes conductive, and a current is permitted to flow in the current mirror circuit successively, and simultaneously, a transistor 21 is cut-off, and an output terminal 11 is in set state.