Based on the amount of e-mail I received after Part 3 of this series, many of you have already guessed that an incremental integrator is really just a delta-sigma modulator (DSM). Well, you’re right! It actually is a continuous-time delta-sigma modulator. "Continuous time" comes from the fact that the integrator comprises resistors, a capacitor, and an op amp. Most commercial DSMs are made with switched capacitor technology. I decided to explain continuous time because most engineers that are unfamiliar with DSM theory are more comfortable with linear circuits and Laplace transforms than they are with switched capacitors and z transforms. Switched capacitors will be a subject for a future column. To read more, click the download link below or visit Electronic Design.
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