Re: Arghhh : Awefully bad noise figures in voltage DACs...

From: John Larkin (jjlarkin_at_highSNIPlandTHIStechPLEASEnology.com)
Date: 09/14/04 

Date: Tue, 14 Sep 2004 09:47:04 -0700

On Mon, 13 Sep 2004 22:35:27 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

>Hi John,
>
>>Oh, as long as I'm raining on your parade, be aware that most serial
>>DACs have nasty clock feedthrough, so expect spikes and perhaps some
>>DC offset while you're clocking the data in.
>>
>>For lowest noise, use an external ref and a DAC that requires an
>>external opamp. All you want inside the DAC is the switches and the
>>thinfilm resistors.
>>
>>
>Or use a sample and hold. SD5400 are really nice for that purpose. The
>S/H needs good RF isolation else the spikes barrel right through. No
>autorouter here.
>
>Regards, Joerg
>
>http://www.analogconsultants.com

LT1597 has a built-in s/h deglitcher, probably better than anything
you can make from parts. It works great as long as you don't clock it
too fast. Also external reference, external opamp, nearly ideal for
this app maybe.

John

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