PURPOSE: To prevent power consumption in pull-up resistors, with high speed operation having maintained, by combining the switching operations of comparators and the logic operation of an R-S FF.

CONSTITUTION: The inverted input terminal of a second open drain type comparator 2 is connected to the non-inverted input terminal of a first open drain type comparator 1. The non-inverted input terminal of the comparator 2 is connected to the inverted input terminal of the comparator 1. A set input terminal S' at an active low state is connected to the output terminal of the comparator 1. A set input terminal R' at an active low state is connected to the output terminal of the comparator 2. A resistor 4 is connected to an inverted output terminal Q' of an R-S FF 3, and a resistor 5 is connected to a non-inverted output terminal Q. The other ends of the resistors are connected to the output terminals of the comparators 1 and 2. In this way, the switching operations of the comparators 1 and 2 and the logic operation of the FF 3 are combined. Thus, the outputs at a logic 'H' level and at a logic 'L' level can be obtained.