PURPOSE: To control whether or not a hysteresis characteristic of an input switching voltage to be provided according to a control signal by controlling a gate of an N-channel MOSFET with a logical circuit output from the output of an inverter and the control signal.

CONSTITUTION: When a control signal input, that is, a node 17 goes to '0' and a node 17 outputting logical inversion of a node 15 and a NOR gate 13 to a node 16 goes to '1', since the NOR gate 13 makes the level of the node 16 to '0' independently of the node 15, an N-channel MOSFET 12 is turned off and an input switching voltage of the inverter 11 is the same voltage as the threshold level in both leading and trailing of the node 14 and the hysteresis characteristic is avoided. Thus, the hysteresis characteristic of the input switching voltage is provided or not provided depending on the control input signal at the same input terminal and the characteristic of the input switching voltage in matching with the property of the input signal is set.