External components improve SAR-ADC accuracy

摘要

It is tempting to use an op amp to directly drive the input of a SAR (successive-approximation-register) ADC. Unfortunately, this configuration can limit circuit performance. An external RC (resistor-capacitor) network better isolates the converter from the driver amplifier and allows greater flexibility in op-amp selection. Getting the best performance from a SAR ADC may be more important than you think. Even if you convert signals that are well below the frequency limitations of the converter and amplifier, you can't ignore the dynamic characteristics of the SAR ADC's input structure.