PURPOSE: To control an input threshold from an external part with being matched to a using condition by selecting the outputs of plural input circuits which are respectively operated by the plural types of the different input thresholds.

CONSTITUTION: A basic inverter circuit is composed of FETs1 and 2. When a '0' level is given to a control terminal 7, this circuit goes to be an inverter circuit, with which only the FETs1 and 2 are operated. When a '1' level is given to the control terminal 7, an additional channel FET3 executes the same operation as the N-channel FET2. Thus, the ability of the N-channel FET2 is improved and the input threshold goes to be low.