Distortion analysis of Miller-compensated three-stage amplifiers

This paper proposes a theoretical approach for evaluating distortion in the frequency domain of three-stage amplifiers adopting two commonly used compensation techniques, namely the nested Miller (NM) and the reversed NM. The analysis is based on appropriate amplifier modeling and on the assumption that the nonlinearity generated by each stage is static. Calculations are thus greatly simplified avoiding complex methods based on the Volterra series. Only dominant contributions need to be taken into account, thereby highlighting those mechanisms generating distortion and their features in the frequency domain. Moreover, the adopted approach provides useful design guidelines and explains why the NM compensation technique allows generally better linearity performance at low frequency and why the reversed NM is best suited to high frequencies. Simulation results with Spectre on two transistor-level CMOS circuits are also provided and found to be in very good agreement with expected results.