Automated design of folded-cascode op-amps with sensitivity analysis

We present a method for optimizing and automating component and transistor sizing in CMOS operational amplifiers. We observe that a wide variety of performance measures can be formulated as posynomial functions of the design variables. As a result, amplifier design problems can be expressed as geometric programs, as special type of convex problem for which very efficient global optimization methods exist. A side benefit of using convex optimization is that a sensitivity analysis is obtained with the final solution with no additional computation. This information is of great interest to analog circuit designers. The method we present can be applied to a wide variety of amplifier architectures, but in this paper we apply the method to a specific two-stage amplifier architecture.