AD/DA conversion

What is the main reason for placing a driver circuit, such as an op-amp, in front of a successive-approximation AD converter?

  1. ATo change the color of the input signal
  2. BTo charge the ADC's internal sampling capacitor quickly and capture the input voltage accurately
  3. CTo reduce the ADC's power consumption to zero
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Answer: B. To charge the ADC's internal sampling capacitor quickly and capture the input voltage accurately

A successive-approximation ADC connects its internal capacitor to the input at the sampling instant. If the source impedance is high, the capacitor does not charge in the short time available and the voltage is not captured accurately. A driver with low output impedance charges the capacitor quickly and accurately.

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More AD/DA conversion questions

  1. Which architecture is used as the internal DAC in many successive-approximation AD converters?
  2. Which is a characteristic of a resistor-string DAC, which connects many resistors in series?
  3. Which AD converter architecture is classified as oversampling?
  4. What does an AD converter (ADC) do?
  5. Which is the most appropriate example of where a DA converter (DAC) is used?