A novel low power hybrid loop filter for continuous-time sigma-delta modulators

A novel low power hybrid (Active-Passive) loop filter using the single amplifier biquad (SAB) filter is presented. This new hybrid loop filter saves power consumption by reducing the number of active elements in the continuous-time sigma-delta modulator. Also, the core biquad filter allows the loop filter of a high-order modulator to be implemented by cascading low-order biquad sections, considerably easing the design and implementation of the high-order continuous-time sigma-delta modulator. The proposed loop filter is a general type of hybrid filter which could be used for the both high and low oversampling ratios (OSRs). Experiment on a 5th-order low pass continuous-time sigma-delta modulator with a bandwidth of 30 MHz is conducted successfully and the results are presented.