Effect of switch charge injection on /spl Sigma//spl Delta/ modulator

Abstract

The effect of switch charge injection on a second-order /spl Sigma//spl Delta/ modulator has been investigated. It has been found that the switch charge injection can cause an error at the output of the SC integrator and that this integrator error can significantly degrade the dynamic range of the oversampling /spl Sigma//spl Delta/ modulator. The integrator error depends on the switch and the integrating capacitor sizes and the common-mode rejection performance of the op-amp. The differential signal at the input of the modulator can also affect the switch charge injection.