Re: Photodiode amplifier noise

John Larkin wrote:
On Sat, 02 May 2009 21:29:47 GMT, James Arthur
<bogusabdsqy@xxxxxxxxxxx> wrote:

John Larkin wrote:
On Sat, 02 May 2009 13:14:40 -0700, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

John Larkin wrote:

[...]

This weekend I'm going to buy a tin of Danish sugar cookies, eat all
the cookies, and build a pA range diode-curve measuring setup into it.
I have a bunch of LMC6001s (Ib is 10 fA typ) to use. The data***
hints somewhere in one of the app circuits that Cin is big. But it's
not specified anywhere.

It's "Danish Butter cookies" :-)

Make sure to _throughly_ clean it before you build anything into it, until wiping shows no grease residue. Else you might experience an impressive meeting of ants in there. BTDT.


The rule seems to be that if Cin is large, don't mention it on the
data***.

Cin is probably largish and usually not used directly:

http://www.postech.ac.kr/ee/paust/paper_link/2007%20Development%20of%20a%20Beam-Profile%20Monitor%20for%20Cyclotron%20MC50.pdf

Interesting; that's vaguely like what I'm tying to do. But I can't
find a data*** on the JU421, even on the Vishay site, so I assume
it's another FormerFet.
www.vishay.com/docs/70248/70248.pdf

Cheers,
James Arthur

Cool. Vishay didn't recognize "JU421".

Nice part for leakage, but with En=30 nv/rthz and Gm=200 uS, it's sort
of the Marching Band of Noise. This guy adds a second one in
differential mode to add bonus noise and lower the gain to boot.


Well, good luck finding one :-)

If you do it'll probably have "DoD pricing".


Why do these scientific types so love differential jfet front-ends?


In electronics they tend to hang on to stuff much longer than we do.

[...]

--
Regards, Joerg

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