Analogue to Digital Converter (ADC)

Analogue to Digital Converter(ADC) Mindaugas J. Abdal M.

Analogue World Everything in the world we live is analogue: • All kind of waves; • All kind of movements; • Even Digital waves are analogue.

Analogue Digital Converters Analogue Digital Converters (ADC) are devices that are used to covert Analogue Signals to Digital ones. By definition ADC are devices with analogue input and digital output. Most of ADC devices are made of poly resistors, amplifier as comparator and coding logic circuit.

Ideal transfer function Figure represents ideal analogue and digital transfer function.

Error There are various problems and error that occurs converting signals: • Input voltage offset • Gain error • INL and DNL

Input voltage offset When that transition happens at some other input voltage, the difference is the offset.

Gain error Another transfer function error. Gain error is seen as a shift in the full-scale code after the offset is corrected

INL and DNL INL – integral non-linearity is a measure of the deviation of the transfer function from the ideal straight line

Extreme DNL DNL - differential non-linearity is any one step size deviation from the ideal

Thanks for your patience ;)

Sources http://www.eetimes.com/document.asp?doc_id=1272445 http://moodle.insa-toulouse.fr/pluginfile.php/2632/mod_resource/content/0/content/images/analog_ad_converter.gif

Analogue to Digital Converter (ADC)