Diff between SINAD and THD+N in ADC Spec

[malli_1729]

Hi!

when i am studying the literature about the ADC and DAC...

i encountered these terms...thing is i didn't found the exact difference between them..
in some material if noise measured bandwidth 0-fs/2 for both...then both these terms will be equal...

what the diff i found is... SINAD will take distorsion which includes harmonics and other frequency components while THD+N will take only harmonics....

Now in datasheets what i found is:
1. Mostly both are not equal
2. SINAD is +ve and THD is -ve always.....

Please tell me what is the difference or relation between these 2 terms....


waiting for the reply...

thanks..

 

[JoannesPaulus]

SINAD=Signal to Noise and Distortion ratio: it includes both the noise (quantization, thermal, jitter, mismatch...) and the distortion of the ADC/DAC. It is a positive number because (hopefully) the power of the ADC is higher than the rest.

THD=Total Harmonic Distortion: it is the ratio of the sum of all the harmonics power to the fundamental tone.

THD+N=THD+Noise: Adds the noise to the THD but it does not add all the spurious tones that are accounted for in the SINAD.

 

[erikl]

See this AD tutorial.