AD/DA conversion

Which correctly describes the SFDR (spurious-free dynamic range) of an AD converter?

  1. AThe ratio of the maximum to minimum input voltage
  2. BThe ratio between the signal amplitude and the largest unwanted frequency component (spur)
  3. CThe ratio of the sampling frequency to the Nyquist frequency
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Answer: B. The ratio between the signal amplitude and the largest unwanted frequency component (spur)

SFDR is the difference in dB, in the output spectrum for a sine-wave input, between the fundamental and the largest spur (unwanted components such as harmonics). In communication ADCs it indicates whether weak signals near strong ones can be detected.

  • A. A ratio of input range limits is not the definition of SFDR.
  • B. Correct. It is the ratio of the signal to the largest spur.
  • C. A ratio of frequencies is not SFDR.
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More AD/DA conversion questions

  1. How many comparisons does an N-bit successive-approximation AD converter basically perform per conversion?
  2. Which correctly describes the acquisition time of a sample-and-hold circuit?
  3. What is the technique of deliberately sampling a signal centered at 70 MHz with a 10 MHz bandwidth at a lower sampling frequency, which also performs frequency conversion?
  4. What is the main purpose of deliberately adding a small noise (dither) before AD conversion?
  5. What is the effect of raising the order of the modulator in a ΔΣ AD converter (for example, from first to second order)?