The SNR (Signal-to-Noise ratio) is a key measure of a data converter’s AC performance. The SNR measures the RMS ratio between the signal amplitude and the noise level, it is the key indicator of how much of the real signal is noise, and higher values are more desirable. THD (Total Harmonic Distortion) is an expression of the distortion effect of a signal’s harmonics on the original signal. THD is important for determining the accuracy of data converters since noise generated by the ADC can not be removed from the conversion results. THD and other nonlinear error sources lower a devices SNR.