A Methodology for Automatic Transistor-Level Sizing of CMOS OpAmps

In this paper, we propose a novel methodology to automate the transistor-level sizing of OpAmps. Given the net list and the specifications of the OpAmp, our methodology automatically produces a set of monomial design equations that can be solved using a geometric programming. The use of monomial models eliminates the overhead of generating elaborate posynomial design equations. The proposed approach is based on the use of circuit heuristics to generate a first order design model, which is then refined by adopting a localized simulation scheme. This approach produces a design that has the accuracy of the BSIM models used for simulation and the advantage of a quick design time. The results of a two stage OpAmp and a Telescopic OpAmp designed in TSMC 0.25μ technology prove the efficacy of our approach.