In this paper, a simulation-based synthesis tool, AMIGO, for analog cell sizing is presented. AMIGO is based upon genetic optimization techniques adapted to circuit sizing. A framework has been developed using TCL/TK language that allows the designer to set the optimization problem, define complex constraint functions, watch the progress of optimization, and finally view results. To increase design reliability a sizing-rule pre-processor is incorporated in the tool to automatically generate topology related constraints specific to analog building blocks. Different approaches of using circuit optimizers are demonstrated through the synthesis of three different analog cells: a latched-type comparator, a folded cascode opamp and a switched-capacitor integrator. AMIGO showed to be a successful synthesis tool that can be part of a more general synthesis/migration flow.