On Wednesday, July 27, 2016 08:55:20 PM Robert LaJeunesse wrote: > The concept of track & hold was well understood in 1966 and documented in > the classic Philbrick Researches amplifier application book, now available > at > http://www.analog.com/library/analogdialogue/archives/philbrick/computing_a > mplifiers.html > > Bob LaJeunesse > > > Sent: Wednesday, July 27, 2016 at 2:15 PM > > From: "Scott Stobbe" <scott.j.sto...@gmail.com> > > To: "Discussion of precise time and frequency measurement" > > <time-nuts@febo.com> Subject: Re: [time-nuts] Precision DACs > > > > The first reference at hand I checked was the ADI Data Converter Handbook, > > 1986. Pg 60 Discusses track & hold, with a reference to the HDD-1206 as > > including track/hold on die. > > > > On Tue, Jul 26, 2016 at 2:46 PM, Richard (Rick) Karlquist < > > > > rich...@karlquist.com> wrote: > > > On 7/25/2016 10:42 PM, Scott Stobbe wrote: > > >> dramatically different due to glitching on code transition. That being > > >> said, they are kept separate not to confuse sources of error. > > > > > > FWIW: > > > > > > The 5071A has a "home brew" DDS that was designed by the late > > > (and great) Robin Giffard. He used what he called a "blanking" > > > circuit that disconnected the DAC during the time period when it > > > is at risk for glitching on code transitions. He described it > > > in terms of some new innovation he had invented. It seemed to > > > me an "obvious" (that loaded word) idea that surely must have > > > been used before. In any event, he was clearly doing something > > > right (as usual). > > > > > > Rick > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the > instructions there. For the particular application a track and hold circuit is not necessary a much simpler circuit that merely disconnects the DAC from the filter input and connects the filter input to ground will suffice. This would result if done properly in a set of constant amplitude glitches at the sample rate which can easily be rejected by the reconstruction filter. The DAC output in effect would be modulated by a square wave with a duty cycle and phase with respect to DAC transitions selected to remove DAC glitches from the filter input. The only effect of this modulation on the filtered output signal will be a small reduction in amplitude to that achievable with a sample and hold style deglitcher.
Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
