Compensation of Finite GBW Induced Performance Loss on a Fifth-order Continuous-time Sigma-Delta Modulator

Nonidealities of active-RC integrators caused by finite gain and finite unity gain-bandwidth product (GBW) of amplifiers directly deviate the transfer characteristic of loop filters and therefore degrade the overall performance of continuous-time sigma-delta ADCs. In this paper the effect of finite GBW on the integrators is reviewed and modeled. The impact of the nonideal integrators on a fifth-order continuous-time sigma-delta modulator is investigated. This paper presents a compensation method combining a coefficient predistortion technique with pole cancellation to reduce the performance loss due to nonideal integrators. Behavioral simulations are conducted on the modulator to verify the effectiveness of the method