How does a sigma-delta ADC work and when is it preferred?

Sigma-delta (delta-sigma) ADC uses oversampling and noise shaping. A comparator samples at high rate (oversampling), digital filter averages samples and increases effective resolution, and noise shaping pushes quantization noise to higher frequencies where it is filtered out. Benefits: very high resolution (16-24 bit achievable), inherent anti-aliasing, excellent linearity, and no missing codes. Trade-off: slower conversion rate than SAR or flash ADCs. Preferred for: precision measurement (temperature, strain, weigh scales), low-frequency signals, and where noise rejection is critical. Most modern precision ADCs are sigma-delta based.