Linearizing digital-analog converters
well i'm assuming you mean "conventional" DACs and not $\Sigma \Delta$ DACs.

in a conventional DAC (like an R-2R ladder or something), there are the micro errors that occur between neighboring DAC codes.  e.g. non-monotonicity.  i think the DSP solution to that is adding a teeny amount dither noise to the value that is output to the DAC.

there is a more macro nonlinearity that one can see in the DAC code to voltage curve.  the curve should be a straight line, but isn't exactly.  to linearize that, you need to compute the inverse curve and put that into a lookup table and process the output to your DAC through the lookup table before outputting it.

all this requires getting to know the specific non-linear faults of your conventional DAC first.  to do that requires an ADC (that the DAC output is connected to) that you trust or many repeated measurements with analog dither and various DC offsets added to the ADC input to smooth out the crap in the ADC.