AD/DA conversion

Learn ADC resolution, the sampling theorem, the differences between flash and successive-approximation types, and quantization error through multiple-choice questions.

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AD/DA conversion: key points

An analog-to-digital converter (ADC) turns analog signals into digital values, and a digital-to-analog converter (DAC) does the reverse. They are used wherever real-world signals meet digital processing, such as sensors, communications and audio.

The basic performance measures are resolution (number of bits) and conversion speed. Understand the sampling theorem, quantization error, and the characteristics of each architecture, such as flash, successive approximation and delta-sigma.

All AD/DA conversion questions (50)

  1. How many output levels can an 8-bit AD converter represent?
  2. What sampling frequency is needed to sample an analog signal containing components up to 20 kHz without aliasing?
  3. Which is a characteristic of a flash AD converter?
  4. Which correctly describes the operation of a successive-approximation (SAR) AD converter?
  5. What is the maximum quantization error of an ideal AD converter? (LSB: the voltage corresponding to one least significant bit)
  6. Which is a characteristic of a delta-sigma (ΔΣ) AD converter?
  7. For a 10-bit AD converter with a full-scale input of 1.024 V, what voltage corresponds to 1 LSB?
  8. What type of filter is used as the anti-aliasing filter placed before an AD converter?
  9. Which is a characteristic of an R-2R ladder DA converter?
  10. What is the role of a sample-and-hold circuit placed before an AD converter?
  11. Which is the approximate formula for the signal-to-noise ratio (SNR) of an ideal N-bit AD converter, set by quantization noise? (For a full-scale sine-wave input)
  12. Which is a characteristic of the dual-slope AD converter often used in digital multimeters?
  13. Which correctly describes the differential nonlinearity (DNL) of an AD converter?
  14. What is the AD converter defect called in which a certain output code never appears no matter how the input changes?
  15. Which is a characteristic of the current-steering architecture often used in high-speed DA converters?
  16. Which metric converts the performance of a real AD converter, including noise and distortion, into the bit count of an ideal ADC?
  17. Which AD converter splits conversion into several stages processed like an assembly line, combining high speed with medium to high resolution?
  18. With simple oversampling and no noise shaping, how much does quantization noise improve when the sampling frequency is quadrupled?
  19. Why does timing fluctuation (jitter) of the sampling clock become a problem when converting high-frequency signals?
  20. When a microcontroller produces an analog voltage by passing a PWM signal through a low-pass filter, what determines the output voltage?
  21. What does 'MS/s (MSPS)', used to express the conversion speed of an AD converter, mean?
  22. In the transfer characteristic of an AD converter, what is the error called when the output deviates from 0 at zero input?
  23. What is an advantage of using a differential input for an AD converter?
  24. In a delta-sigma AD converter, which digital circuit converts the fast, coarse quantized output into high-resolution data at a lower sampling rate?
  25. What is the brief spike-like error that appears at the output of a DA converter at the moment the input code changes?
  26. Which architecture runs several AD converters alternately with slightly staggered timing to achieve a high overall sampling rate?
  27. What is the main reason for placing a driver circuit, such as an op-amp, in front of a successive-approximation AD converter?
  28. Which architecture is used as the internal DAC in many successive-approximation AD converters?
  29. Which is a characteristic of a resistor-string DAC, which connects many resistors in series?
  30. Which AD converter architecture is classified as oversampling?
  31. What does an AD converter (ADC) do?
  32. Which is the most appropriate example of where a DA converter (DAC) is used?
  33. For AD converters with the same input range, what happens when the resolution (number of bits) is increased?
  34. Which correctly describes "sampling" in AD conversion?
  35. What is the error caused by quantization in AD conversion called?
  36. What is the sampling frequency of a music CD?
  37. Which correctly describes the integral nonlinearity (INL) of an AD converter?
  38. Which correctly describes the gain error of an AD converter?
  39. What does it mean for a DA converter to be monotonic?
  40. What is the drawback of a binary-weighted resistor DAC, which assigns a different resistor (R, 2R, 4R, ...) to each bit?
  41. How many comparators does a 3-bit flash AD converter need?
  42. If a 10 kHz sine wave is sampled at 12 kHz without an anti-aliasing filter, at what frequency does it appear?
  43. Which correctly describes the SFDR (spurious-free dynamic range) of an AD converter?
  44. How many comparisons does an N-bit successive-approximation AD converter basically perform per conversion?
  45. Which correctly describes the acquisition time of a sample-and-hold circuit?
  46. 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?
  47. What is the main purpose of deliberately adding a small noise (dither) before AD conversion?
  48. What is the effect of raising the order of the modulator in a ΔΣ AD converter (for example, from first to second order)?
  49. In a time-interleaved ADC that alternates between several ADCs, what problem is caused by mismatches in offset, gain and timing between the individual ADCs?
  50. Which correctly describes the "offset binary" code used in ADCs that handle both positive and negative voltages?

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