PURPOSE: To generate a membership function of an optional shape with the combination of a digital circuit and a transistor circuit by providing a comparator on each of the 1st - n-th processing parts to compare the analog voltage with the input voltage together with a D/A converter.

CONSTITUTION: Two transistors TR i1 and TR i2 of a processing circuit 10-i have their emitters connected in common, and the emitter voltage is expressed as Vi = Vsi + VEB or Vi = V1 + VEB. Therefore the output of a TR i3 is shown as Voi = Vsi + VEB - VBE or Voi = Vi + VEB - VEB. In such conditions, VEB = VEB is satisfied for TR i1, i2 and i3 respectively. Thus Voi = Vsi (Vsi ≤ V1) and Voi = V1 (Vsi > V1) are satisfied. This can be applied to all outputs V01 - V0n and the prescribed output characteristic is obtained. Furthermore this output characteristic is varied in response to the input voltage V1.