Input common-mode voltage feedback circuit for continuous-time sigma-delta analog-to-digital converter

摘要

A novel circuit is used to monitor the common-mode voltage at the summing junctions of the first integrator in a continuous-time ΣΔ ADC, wherein the circuit produces a control voltage which adjusts the quiescent current of the feedback DAC to compensate for any common-mode offset current. Since the adjustment takes place within the feedback DAC, there is no extra noise added to the differential signal path. The implementation provides for no degradation to the SNR of the converter.