Which statement correctly compares the SAR and sigma-delta ADC architectures in terms of resolution, speed, and noise shaping?

• A. SAR provides high resolution with oversampling; sigma-delta moderate speed
• B. SAR moderate speed, mid-high resolution; sigma-delta high resolution with oversampling, good for audio
• C. SAR is slow and low resolution; sigma-delta is fast with low resolution
• D. SAR uses only analog processing; sigma-delta uses only digital processing

Answer: (B)

The main idea is how these two ADCs trade off resolution and speed and how they handle quantization noise. A SAR converts by a binary search using a DAC and comparator, which gives a fast, deterministic conversion with good, programmable resolution depending on bit depth. It doesn’t rely on oversampling, so the noise shaping benefits aren’t used, giving a solid balance of speed and resolution suited for many high-speed, mid-to-high resolution needs. A sigma-delta ADC, on the other hand, oversamples the input a lot and shapes the quantization noise so most of it sits outside the signal band. This allows very high effective resolution, which is why sigma-delta is favored for audio and other low-bandwidth, high-precision applications. The trade-off is speed: the heavy oversampling limits the maximum sample rate for a given resolution compared with a SAR.

So the statement that captures these points best is that SAR offers moderate speed with mid-to-high resolution, while sigma-delta provides high resolution through oversampling and noise shaping, well-suited for audio. Other descriptions blur these roles, such as attributing oversampling to the SAR, claiming sigma-delta is fast with low resolution, or saying one uses only analog or only digital processing.