A new method for harmonic distortion analysis in class-AB stages

In this brief, a new method for analytically evaluating the harmonic distortion (HD) in class-AB stages is introduced. It is based on modeling each push-pull device in the stage with a different third-order polynomial. The coefficients of these polynomials are then evaluated by straightforward computations or by pencil-and-paper analysis on the transcharacteristic of the stage. The resulting theory was validated by simulations and is able to predict the HD behavior of a class-AB stage over a wide range of input values. An example of the use of the theory for pencil-and-paper analysis is also given.