AbstractDARWIN is a synthesis tool for generating sized net lists of CMOS op amps from performance specifications and process parameters. the synthesis process starts with an initial set of randomly generated op amps. Owing to genetic operator ‘crossover’ and ‘mutation’, the population of op amps evolves to a population in which several op amps meet the required specifications. During the synthesis process the circuit topology and circuit parameters (capacitor values, bias currents and transistor lengths and widths) evolve simultaneously with the final solution. the circuit description we use in the genetic algorithm ensures that all intermediately generated circuits possess a number of qualities that are required for a correct functioning of the circuit. Synthesis experiments have shown that DARWIN is capable of synthesizing functional circuits without the need of much design knowledge.