PURPOSE: To generate a symmetrical triangular/trapezoidal membership function by setting the central position of the membership function, the inclination of an oblique side and height.

CONSTITUTION: In an addition circuit 1, input VIN is shifted in the direction of a lateral axis by the central position voltage Vx of the membership function, the inclination is decided by the ratio of a resistance Ro and a variable resistance VR, and input VIN is outputted to a point A in an inverted form. At the output B-point of an inversion circuit 2, the output of the point A is inverted as against the lateral axis and it is outputted. The outputs of the points A and B, and the upper setting point VW of the trapezoidal membership function are inputted through an input buffer 3 to addition circuits with clip circuit 4 and 5 in a next stage. In an addition circuit 6, the outputs of points C and D are synthesized and output is shifted in the direction of a vertical axis by VH. The output of a point E is inverted by an inversion circuit 7 and the final membership function is outputted as VO.