A novel nonlinear settling model of OTA for high-resolution switched-capacitor sigma-delta modulator design

A novel nonlinear settling model of OTAs in SC integrators is presented. Using this accurate model, the requirement for OTAs in high-resolution sigma-delta modulator A/D converters is relaxed. Firstly, a signal-dependent nonlinear settling time constant is derived based on the circuit-level analysis. Then, a modified nonlinear settling algorithm is proposed by including the obtained nonlinear settling time constant. Finally, a high resolution fourth-order cascaded sigma-delta modulator is simulated and results are compared with other approaches.