Re: AD5791

On 2024-06-06 13:57, john larkin wrote:

On Thu, 06 Jun 2024 10:15:45 -0700, boB <boB@K7IQ.com> wrote:
 

On Tue, 04 Jun 2024 10:48:00 -0700, john larkin <jl@650pot.com> wrote:
>

https://www.analog.com/en/products/ad5791.html
>
That's an amazing part. 20 bit DAC with 1 PPM accuracy and 0.05 PPM
per degree C tempco.
>
My main gripe is its 3.4K output impedance, which makes a lot of
Johnson noise. I suppose I could run a bunch in parallel.

>
>
Nice part but costs way too much for any products we make.
>
boB

 What do you make?
 We live on the lunatic fringe of electronics, things that are really
hard to do, things with extreme exponents. It makes money because it
has little competition, but the money is a side effect. I do it
because it's fun.
 There must be something cool that we can do with a 1 PPM accurate DAC.
 TI has a 20-bit delta-sigma DAC that's about $12, but it's only linear
to 15 PPM. I don't understand how a d-s DAC or ADC can even be that
good. It would seem to need femtosecond edge accuracies inside.
 

I expect that the deterministic part of the jitter gets pushed out to high frequency by the noise shaping.
Random jitter you'd have to deal with by averaging.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com