PURPOSE: To select and set simply an input terminal in a pull-up or a pull-down at need by a method wherein the proper use of the pull-up and the pull-down is performed utilizing the 2 states of a CMOS inverter.

CONSTITUTION: An input terminal 2 of an input circuit 1 constituted of two stages of inverters is connected to an output node of a CMOS inverter 10 provided with a P-channel pull-up transistor Qa and an N-channel pull-down transistor Qb. When a selective control terminal 3 is fixed in a state that a selective control voltage at an 'L' level is applied to the terminal 3, the Qa is turned on, the Qb is turned off and the terminal 2 is pulled up by the on resistance of the Qa. Contrast to this, in case the terminal 3 is fixed in a state that a selective control voltage at an 'H' level is applied to the terminal 3, the Qa is turned off, the Qb is also turned on and the terminal 2 is pulled down by the on resistance of the Qb.