A MASH modulator with digital correction for amplifier finite gain effects and C-ratio matching errors

An alternative approach to remove the effects of amplifier finite gain and C-ratio mismatches encountered in a MASH delta-sigma modulator is presented. By adding a digital correction term to the output of the digital noise cancelation filter, the parasitic quantization noise terms can be removed for all but the final stage, eliminating the lower-order quantization noise terms due to non-ideal integrators. Using this technique, the MASH can approach the performance of an ideal 3/sup rd/ order modulator. We have confirmed an SNR+THD of 105.6 dB via a behavioral simulation of the MASH using an amplifier open-loop gain of only 500 and capacitor matching errors as large as of 1.0%.