Accurate estimation of high-frequency harmonic distortion in two-stage Miller OTAs

A simple and comprehensive study of the high-frequency harmonic distortion of two-stage Miller-compensated CMOS OTA used in inverting configuration is presented. An improved extension of a symbolic approach recently proposed by the authors is adopted here. As a result of a better formalisation, inaccuracies incurred by the original formulation can be avoided and closed-form expressions of second- and third-order harmonic distortion factors are derived, whose precision extends well beyond the amplifier´s gain-bandwidth product. The correctness of both this approach and the expressions derived was confirmed by comparison with computer simulations at transistor level.