An advanced S/sup 3/I sigma-delta modulator with reduced distortion

The paper presents several novel improvements to current-mode sigma-delta modulators. The focus is put on the first integrator arrangement as the most limiting block in sigma-delta front ends. An autozeroing function is used to reduce low-frequency noise and offsets generated by current mirrors, and S/sup 3/I integrator with extended saturation voltage range is developed. A distributed input feedforward path is discussed and adopted in a third-order cascade sigma-delta modulator.