A novel approach to the calculation of nonlinear harmonic distortion coefficients in BJT differential amplifiers

Abstract

Abstract The base-driven BJT differential pair is analysed, taking the Early effect into consideration and using a different model. Harmonic distortion coefficients are calculated and an accurate analytical expression representing the total harmonic distortion is proposed. It is shown that this expression leads to a minimum point in total harmonic distortion which cannot be obtained with the SPICE modified Gummel-Poon model that underestimates the contribution of the Early effect, and therefore accurate simulation by SPICE is not possible.