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NNTP-Posting-Date: Fri, 07 Jun 2024 02:19:23 +0000
Subject: Re: AD5791
Newsgroups: sci.electronics.design
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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Message-ID: <ab603e30-c36f-b39a-ad2e-0a34f0eced22@electrooptical.net>
Date: Thu, 6 Jun 2024 22:19:22 -0400
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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