If the DAC update rate isn't excessive a 2nV-sec glitch is unlikely to produce a significant perturbation at the output of the lowpass filter following the DAC.
Bruce > On 16 October 2019 at 21:01 Attila Kinali <att...@kinali.ch> wrote: > > > On Wed, 16 Oct 2019 15:04:31 +1300 (NZDT) > Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > > > Consistency of the glitch independent of DAC output is more important than > > its size. A constant amplitude glitch occurring at the dac update rate is > > more benign in its effect than a glitch whose amplitude varies with DAC > > output. > > Yes. But it's actually not that bad. The glitch in the DAC is due to > the CMOS switches in the DAC switching. Due to symmetry of the operation > the glitch going from code A to code B will be the (almost) inverse of going > from code B to code A. Which means they should (almost) cancel. > > I can't find my notes from when I calculated this, but I remember that > using an external CMOS switch had the same order of magnitude of uncertainty > as using the DAC itself. And a few other effects would be also very close > in magnitude. My conclusion was, considering that the back-of-envelope > calculation of errors would result in a few bits more than necessary, > the added complexity of using an external CMOS switch was probably not > worth it. Of course, to be sure one would need to build both variants > and measure them. Unfortunately, I don't have the means to do that. > > Also, my guesstimate would be that using two DACs with metal-foil > resistors for weighting would probably result in lower non-linearity. > But the problem here is that the resistors add quite a bit of noise > which in turn has to be accounted for. > > Attila Kinali > > -- > <JaberWorky> The bad part of Zurich is where the degenerates > throw DARK chocolate at you. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
