A X-coupled differential single-opamp resonator for low power continuous time ΣΔ-ADCs

Continuous time sigma-delta ADCs usually are designed with noise transfer functions containing conjugate complex zeros to extend the usable bandwidth. Traditionally, these zeros are implemented with a resonance generated by local feedback around two integrators. Recently a loop filter topology with reduced number of opamps based on modified Twin-T single-opamp resonators has been proposed with the aim to reduce power dissipation. In this work, we propose an alternative differential single opamp resonator with cross-coupled feedback, which is more compact, more power efficient, more robust to parasitics and more linear than the Twin-T based single-opamp resonators.