Systematic Design For Multistage Feed-forward Op-amp For High-Speed Continuous-Time ∑Δ ADCs.

This paper presents a systematic design methodology for multi-stage feed-forward op-amps used in the active filters of continuous time $\Sigma\triangle$ ADC. This methodology can provide the specifications of each stage in the op-amp (from 2 stages to 4 stages) based on the required ADC specifications and can provide an estimate of the Signal to Noise Ratio (SNR) taking into consideration the effect of the transfer function of the opamp. This method is then validated on a Lowpass and Bandpass $\Sigma\triangle$ ADCs.