To use a differential logic and to make power consumption lower without lowering a switching speed of a circuit nor increasing sensitivity to interference by serially connecting at least one of switching stages to a subsequent switching stage.

At least one switching stage 12 from among switching stages 2, 3 and 12 is serially connected to a subsequent switching stage 3 so as to reduce the number of current paths that are connected in parallel, while maintaining the dimensions of supply voltages Vcc and Vee, input voltages inp and inn and output voltages outp and outn. In such a case, power consumption reduces by more than power consumption of a conventional circuit without changing the voltages Vcc and Vee and input and output conditions. This is accomplished by providing a parallel combination of only two branches, instead of a parallel combination of three conventional emitter followers, because one branch of the parallel combination comprises two serial emitter followers 12 and 3 and power consumption of the two branches does not change.