PURPOSE: To provide the transistor input circuit of one terminal and three values capable of not consuming power except for the time when an input terminal is opened and capable of being applied to a low power consumption type integrated circuit relating to the transistor input circuit of one terminal and three values.

CONSTITUTION: A first circuit 20 is provided with a first input terminal 1, a first output terminal 3 and a control terminal 8. For a second circuit 21, a second input terminal 21i is connected to the input terminal 1 of the first circuit 20 and the output terminal 21j is connected to the control terminal 8 of the first circuit 20. When the input terminal 1 of the first circuit 20 is opened, the second circuit 21 supplies a high level voltage for fixing the voltage of the output terminal 3 of the first circuit 20 at a low level voltage to the control terminal 8 and when the voltage of the input terminal 1 is at the high level or the low level, supplies a control voltage for outputting a logical level voltage corresponding to the logical level of the voltage of the input terminal 1 from the first output terminal 3 to the control terminal 8.