vivkr
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Hi,
Mismatch is equally likely to happen in a resistor ladder as in a current-steering DAC. Apart from random mismatch which you can reduce with large sized resistors, and excellent common-centroid layout with dummies, there will also be systematic mismatch which you will see if your layout is not good.
Have you measured several parts? Do you see the same nonlinearity profile (more or less) for all of them? If yes, then your layout is to blame. If you see random profiles for nonlinearity, then it is residual mismatch, to reduce which you would need to make the resistors larger.
I suspect you have layout issues. Measure nonlinearity for 20-30 parts and then compare the profiles.
Regards, Vivek
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