Analytical Expressions for the Distortion of Asynchronous Sigma–Delta Modulators

This brief investigates the commonly used asynchronous sigma-delta modulator, which consists of a Schmitt trigger and a continuous-time loop filter. A detailed analysis is presented to accurately predict the distortion of such modulators. The extracted expressions are compared with simulation results, and they illustrate an excellent match. The results are also compared with a previous work by Roza, and they show a drastic improvement in accuracy.