AD/DA conversion

What is the role of a sample-and-hold circuit placed before an AD converter?

  1. ATo amplify the input signal
  2. BTo hold the input voltage constant while AD conversion is performed
  3. CTo generate a clock signal
Show answer and explanation

Answer: B. To hold the input voltage constant while AD conversion is performed

AD conversion takes a certain amount of time, and if the input voltage changes during that time, it cannot be converted correctly. A sample-and-hold circuit captures the input voltage at one instant on a capacitor and holds it until conversion is complete. It is essential in successive-approximation ADCs and others.

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More AD/DA conversion questions

  1. 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)
  2. Which is a characteristic of the dual-slope AD converter often used in digital multimeters?
  3. Which correctly describes the differential nonlinearity (DNL) of an AD converter?
  4. What is the AD converter defect called in which a certain output code never appears no matter how the input changes?
  5. Which is a characteristic of the current-steering architecture often used in high-speed DA converters?