Degradation of alias rejection in continuous-time bandpass delta-sigma converters due to weak loop filter nonlinearities

We show that the nonlinearity of the first integrator's operational transconductance amplifier(OTA) significantly degrades the alias rejection of a bandpass CT∆ΣM in the presence of OTA parasitics. We derive the expression for alias rejection when the OTA used in the first integrator is realized as a two stage feed-forward compensated structure. Simulation results confirm the theory.