Various DAC have different full scale current or even an adjustable full scale current. Why this difference and what are the advantages of a small or large full scale current?
As a differential current steering DAC is constantly outputting a DC full scale current of I_full-scale, the primary reason to provide a scalable full scale current is to minimize power consumption.
The direct effect of changing the full scale current is that, if nothing else changes, the full scale signal output will change proportionally. However, if one changes the load resistor inversely proportionally to the change in full scale current, the output signal level would remain the same though.
Changing the full scale current has also the effect of changing the noise floor of the signal. Intrinsically, the whole spectrum will move down (signal and noise) as the full scale current decreases but as the noise floor gets into the thermal noise of the signal chain, the dynamic range of the DAC will become affected.
Finally, distorsion can also be affected by the change in full scale current. However, this phenomenon is dependent on the optimum design point chosen for the DAC and generalities are hard to define.
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