Improved Macromodeling Helps Sizing of Multi-stage Op Amps – A Case Study

Abstract Behavioral modeling of analog integrated cir- cuits has many applications. When used for sizing, ac- curacy of compact models can be used for directly eval- uating part of circuit performance targets, helping to quickly forming initial sizing for further iterations. In this paper we elaborate on modeling improvement of the current buffer (CB) compensation recently received attention in multi-stage operational amplifier (op amp) designs. Limitation in conventional models is pointed out and improvement is proposed. We demonstrate via cases that the improved macromodels can leverage the efficiency of sizing by incorporating the gm/ID method.