On Chopper Effects in Discrete-Time $\Sigma \Delta$ Modulators

Analog-to-digital converters based on ΣΔ modulators are used in a wide variety of applications. Due to their inherent monotonous behavior, high linearity, and large dynamic range, they are often the preferred option for sensor and instrumentation. Offset and flicker noise are usual concerns for this type of applications, and one way to minimize their effects is to use a chopper in the front-end integrator of the modulator. Due to its simple operation principle, the action of the chopper in the integrator is often overlooked. In this paper, we provide an analytical study of the static effects in ΣΔ modulators, which shows that the introduction of chopper is not transparent to the modulator operation and should thus be designed with care.