Harmonic distortion analysis via perturbation methods

The most commonly-used analytical tool for predicting distortion is Volterra series. Analog circuits that yield to Volterra series analysis can also be analyzed with perturbation theory. In fact, perturbation methods can even be used to study certain distortion phenomena that are inscrutable with Volterra series analysis. This paper describes some elementary results that come from applying perturbation methods to simple first-order circuits.