Feed-forward path and gain-scaling - a swing and distortion reduction scheme for second order sigma-delta modulator

This paper proposed a two second-order sigma-delta modulator schemes for reducing the swing at the output of the first and the second integrators. The new schemes used feed-forward path to eliminate the term due to the input signal at the output of the first and second integrators completely. Hence, the integrators are processing only the quantization noise that is uncorrelated to the input signal. This paper also proposed a condition for scaling each integrator gain to further reduce the first integrator output swing using gain-scaling technique. Both techniques will make the modulator less sensitive to any harmonic distortion from the opamp used in the integrator.