Abstract: A semiconductor integrated circuit device is supplied with internal circuit operating voltage and/or internal circuit ground potential from the outside through a unidirectional element, and the device is provided with a unidirectional element disposed so as to pass current flowing from a circuit internal ground potential point toward an input and/or output terminal and/or a unidirectional element disposed so as to pass a current flowing from the input and/or output terminal toward an internal circuit operating voltage point. According to the above, signals supplied to the input and/or output terminal can be enlarged without being restricted by the level of the internal circuit operating voltage and/or the internal circuit ground potential by virtue of the switching function of the unidirectional elements.