A General Time-Domain Method for Harmonic Distortion Estimation in CMOS Circuits

This article presents a general, time-domain harmonic distortion estimation method, applicable to linear CMOS circuits characterized by weakly nonlinear behavior, ranging from amplifiers, and transconductors to filters, with any number of stages. It offers a compact, fast, and systematic way to model circuits as a structure of interconnected G _m -stages, and estimates the harmonic distortion at every circuit node, providing insight into the distortion contribution of every stage. The method uses a more involved model for each G _m -stage that also accounts for the dependence of its output current on cross-products of its input and output voltages, improving significantly the distortion estimation accuracy. The proposed method is easily implemented in MATLAB, and intends to be integrated as a tool in EDA suites to speed-up distortion estimation. A number of examples are presented, illustrating the application of the method and validating its accuracy via comparison with Cadence Spectre simulation.