An Intelligent System for the Design of Analog Integrated Circuits

Abstract

Conventional CAD tools are brought into use late in the design process after much of the functional operation of a circuit has been defined. A new type of design environment must be created to aid the engineer from goal creation all the way to silicon fabrication. Symbolic equation generation is an area of active research which will extend the application of computers earlier into the design process. A tool for equation development in an interactive design environment is described. The system successfully meets the following three constraints for a useful interactive symbolic analysis system. First, it is quicker than an engineer at generating the equations. Like the engineer it is capable of handling large circuits without an exponential growth in calculation time. Secondly, it produces equations simplified in the same form as the design engineer would create by hand. Finally, the entire system is easily modified and expanded by the design engineer personally. The equation developing system is based upon the Norton equivalent circuit approximation. Norton equivalence is used to keep the equations linear, to decouple the circuit into more manageable building blocks, and because it results in equations similar to those developed by engineers in hand analysis. A prototype system was implemented using a rule based development program called CLIPS. The rule based system environment makes extension to the system by non-programmers a simple task. This paper explains the motivation, theory, and implementation of the symbolic analysis system.