AD/DA conversion

With simple oversampling and no noise shaping, how much does quantization noise improve when the sampling frequency is quadrupled?

  1. ANo improvement
  2. BAbout 6 dB (about 1 bit)
  3. CAbout 24 dB (about 4 bits)
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Answer: B. About 6 dB (about 1 bit)

The total quantization noise is fixed, so raising the sampling frequency spreads it thinly over a wider frequency range. In-band noise decreases by 10 log₁₀(4) ≈ 6 dB, an improvement of about 1 bit. Delta-sigma converters combine this with noise shaping to achieve much larger improvements.

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More AD/DA conversion questions

  1. Why does timing fluctuation (jitter) of the sampling clock become a problem when converting high-frequency signals?
  2. When a microcontroller produces an analog voltage by passing a PWM signal through a low-pass filter, what determines the output voltage?
  3. What does 'MS/s (MSPS)', used to express the conversion speed of an AD converter, mean?
  4. In the transfer characteristic of an AD converter, what is the error called when the output deviates from 0 at zero input?
  5. What is an advantage of using a differential input for an AD converter?