PURPOSE: To decrease the number of input terminals by handling an input to a semiconductor integrated circuit on a analog basis.

CONSTITUTION: An input Vi set at the voltage-division ratio of a variable resistor 2 and a fixed resistance 3 is determined by resistance groups 5W13, and then compared by a comparator 22 with a voltage V, swept by signals C1WC8 generated by decoding outputs Q1, Q2 and Q3 of a counter 23 and selected through transmission gates 14W21; and its comparision output V0 changes from an earth potential "1" to a VSS potential "0" to close a gate 25 for a clock CL inputted to the counter, and at the same time counter outputs Q1, Q2 and Q3 held in current states are inputted as the analog-digital conversion value of the analog input Vi.