ABCs of ADCs - Analog-to-Digital Converter Basics (PDF)

SFDR - Spurious FreeDynamic Range0-10-20-30-40-50-60-70-80-90Signal65dB SFDRHighest “Spur”24Spurious Free Dynamic Range (SFDR) is the difference between the value of the desiredoutput signal and the value of the highest amplitude output frequency that is not present in theinput, expressed in dB. Some ADC suppliers ignore harmonics when specifying SFDR, but thispractice is valid only if those harmonics were present at the ADC input.Because SFDR is expressed in dB below the fundamental, it is sometimes expressed innegative dB. However, since it is a range, it should be expressed in positive dB.ABCs of ADCs - Rev 3, June 2006Authored by: Nicholas “Nick” Gray24Copyright © 2003, 2004, 2006 National SemiconductorCorporationAll rights reserved