ABSTRACT
Continuous-time analog techniques offer a very good relation between area occupation and inference speed. This is achieved, on the one hand, by eliminating the need for control signals and, on the other hand, by fully exploit ing the potentiality of the basic element of a MOS integrated circuit which is the MOS transistor. Continuous-time analog techniques were employed to im plement the first analog fuzzy integrated circuits. This is described in Section 7.1 The chapter continues in Section 7.2 with the description of three basic archi tectures of fuzzy integrated circuits that process the rules in parallel. These ar chitectures can be implemented with analog or digital techniques. The advantage of using continuous-time analog techniques is that the operations re quired within each rule can also be realized in parallel with circuits that admit multiple inputs, consume low power, and occupy small silicon area. After the different architectures have been explained, the next three sections are ded icated to describing the design of the basic building blocks in these architec tures. Section 7.3 shows the circuits (MFCs) that can be employed in the fuzzification stage to generate the membership functions of the fuzzy sets cov ering the input universes of discourse. Section 7.4 describes the circuits that can be employed in the rule processing stage to implement the basic t-norm and s-norm operators of a fuzzy system, such as minimum, maximum, product (scaling), and addition. Finally, the circuits required in the output stage of a fuzzy system are analyzed in Section 7.5. As a summary of the chapter, Section 7.6 describes the design of a CMOS programmable prototype that implements a simplified fuzzy inference system with 9 rules and 2 inputs. Experimental results of this prototype illustrate the operations performed in each stage as well as the input/output surfaces obtained for different programmable codes. This chapter focuses on MOS technologies, which are cheaper than bipolar ones and fully compatible with digital designs. Also, some bipolar circuits are described to provide the reader with an unified view of this design style.
