PURPOSE: To supply appropriate current driving capacity to an output terminal by selecting a buffer connected between input and output control circuits corresponding to an external load connected to the output terminal by the input and output control circuits, and varying the number of buffers located between each input terminal and out put terminal.

CONSTITUTION: When the external load with reference value is connected to both output terminals 1-2 and 2-2, three buffers are allocated uniformly. When the external load less than a reference value is connected to the output terminal 2-1 and the one higher than that to the output terminal 2-2, the input control circuit 3 connects the input terminal 1-1 to a buffer input terminal 8-1, and also, connects the input terminal 1-2 to buffer input terminals 8-3, 8-4, 8-5, and 8-6. In such a way, it is possible to divert an unused buffer in the output terminal to which the external load less than the reference value is applied to the one to increase the current driving capacity of the output terminal to which the external load higher than the reference value is applied, and to heighten the working efficiency of a driving transistor.