PURPOSE: To make two contradictive characters such as reduction of power sonsumption and speed up etc. improve compatibly by controlling variably equivalent resistance value of a resistance element in a logic circuit by logical output.

CONSTITUTION: When logical input in is H, a phase split step transistor TRQ2 becomes on, and logical output out becomes L, and FETM4 becomes off consequently. Thereby, equivalent value of a resistance element that forms load of collector side of the TRQ2 becomes high and power consumption is lowered. On the other hand, input in becomes H→L, TRQ2 becomes on→off and output out becomes L→H. At this time, the FETM4 is changed from off to on the way the output out rises up from L to H. Thus, equivalent value of the resistance element that forms load of collector side of the TRQ2 becomes low in a moment. Consequently, change from L to H of the output out becomes sharp. Thus, characteristics of two contradictive characters can be improved compatibly.