PURPOSE: To construct a comparator circuit of a smaller number of circuit elements to output the results of a judgment on difference in comparison be tween an input current and a reference current.

CONSTITUTION: A two-stage construction of a preamplifier circuit and a comparison/latch circuit divided in the past are consolidated into one stage. In an amplification mode, a latch circuit drive signal is set to 'L' to turn ON MOS transistors M1 and M4 so that an input voltage VIN is applied to the base of a third bipolar transistor Q3. In a comparison/latch mode, a latch circuit drive signal is set to 'H' to turn OFF the MOS transistors M1 and M4 while MOS transistors M2 and M3 are turned ON.