Re: Noise in tantalum SMT caps?

Spehro Pefhany wrote:
On Fri, 18 Jan 2008 18:12:34 -0800, the renowned John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, 18 Jan 2008 16:29:19 -0500, Spehro Pefhany
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

Any idea what noise I'd see in a tantalum 150uF cap with 1.25V across
it?


Best regards, Spehro Pefhany
I'd guess just the thermal noise of the esr, which is only a couple
tenths of an ohm maybe.

John

No sub-10Hz voltage noise as aluminum electrolytics under bias are
supposed to have?

I'm looking at a design (not my own) where there's an RC on the output
of a voltage reference feeding a Sigma-Delta 24-bit ADC. The R is
causing a full scale gain error of, oh, 17bits. 8-( Over 1%.


Ouch! Did they split the grounds? That can cause part of it. I've never had a case where that brought the ENOB down this much, but it put a measurable crimp into it.


Is the reference input current constant with input voltage?
Temperature? I doubt it. 8-(


There's probably a lot more that's not constant.

--
Regards, Joerg

http://www.analogconsultants.com/
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