PURPOSE: To define circuit function with programming and to easily correspond to a later circuit change by connecting an interval between the input and output terminal of an operational amplifier and a circuit element with a programmable switch means.

CONSTITUTION: The intervals between input and output terminals 1a∼1c of an operational amplifier 1 and circuit elements R1∼R5, C1∼C3 and TR1 are connected by programmable switch means S1∼S11. Namely, the plural circuit elements for input, which are connected to the input and output terminals 1a∼1c, or plural circuit elements for feedback are prepared in advance with the operational amplifier 1 as a center and those elements are arbitrarily selected by the programmable switch means S1∼S11. Thus, the desired circuit function is realized and the selection can be changed by the re-programming of the switch means S1∼S11. Then, the change of the circuit function can be easily executed.