A synthesis system for analog circuits based on evolutionary search and topological reuse

Abstract

We present a method for automated synthesis of analog circuits using evolutionary search and a set of circuit design rules based on topological reuse. The system requires only moderate expert knowledge on part of the user. It allows circuit size, circuit topology, and device values to evolve. The circuit representation scheme employs a topological reuse-based approach-it uses commonly used subcircuits for analog design as inputs and utilizes these to create the final circuit. The connectivity between these blocks is governed by a well-defined set of rules and the scheme is capable of representing most standard analog circuit topologies. The system operation consists of two phases-in the first phase, the circuit size and topology are evolved. A limited amount of device sizing also occurs in this phase. The second phase consists entirely of device value optimization. The design of the evaluation function-which evaluates each generated circuit using SPICE simulations-has also been automated to a great extent. The evaluation function is generated automatically depending on a behavioral description of the circuit. We present several experimental results obtained using this scheme, including two types of comparators, two types of oscillators, and an XOR logic gate. The generated circuits closely resemble hand designed circuits. The computational needs of the system are modest.