Nonlinearities in SC delta-sigma A/D converters

The effects of using nonlinear low-gain opamps in switched-capacitor delta-sigma modulators are analyzed. Using unconventional topologies, the state variables are made essentially uncorrelated with the input signal, hence opamp nonlinearity will cause very little harmonic distortion. Nonlinearity errors, which are uncorrelated with the input, are called non-harmonic distortion. Using a correlated-double-sampling integrator, the non-harmonic distortion can be reduced to a level where other errors dominate