AD/DA conversion

Which correctly describes the operation of a successive-approximation (SAR) AD converter?

  1. AIt integrates the input voltage for a fixed time and measures the discharge time
  2. BStarting from the most significant bit, it compares the input voltage with the output of an internal DAC and decides one bit at a time
  3. CIt achieves high resolution through oversampling and noise shaping
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Answer: B. Starting from the most significant bit, it compares the input voltage with the output of an internal DAC and decides one bit at a time

A successive-approximation converter asks, starting from the most significant bit, whether the input is larger than the internal DAC output, deciding one bit at a time like a binary search. An N-bit conversion needs N comparisons. Its good balance of speed, accuracy and power makes it widely used, for example in microcontroller ADCs. Measuring by integration is the dual-slope type, and oversampling is used by the delta-sigma type.

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More AD/DA conversion questions

  1. What is the maximum quantization error of an ideal AD converter? (LSB: the voltage corresponding to one least significant bit)
  2. Which is a characteristic of a delta-sigma (ΔΣ) AD converter?
  3. For a 10-bit AD converter with a full-scale input of 1.024 V, what voltage corresponds to 1 LSB?
  4. What type of filter is used as the anti-aliasing filter placed before an AD converter?
  5. Which is a characteristic of an R-2R ladder DA converter?