What the heck is going on with TI's Burr Brown parts manufacturing? - was Photodiode case

Christopher R. Carlen wrote:
Winfield Hill wrote:
John Larkin wrote:

Bootstrapping is likely to cause more troubles than it's worth.

Sheesh, we seem to be on the opposite side of several issues
today. In fact, bootstrapping, properly done, which isn't very
hard, works marvelously well. Keep in mind some PDs have VERY
high capacitance, even when back biased to the max. (For example,
some of those used for UV detection: try 400pF at 10V bias.) At
high freqs one is bitterly fighting i = w-en-Cin noise, and there's
a limit to how far down one can push en with available IC opamps.
But one can easily make a 0.8nV 80MHz-bandwidth guard / follower
(e.g., with a bf862 JFET input stage), dramatically lowering Cin
in the noise formula above. I can be a real lifesaver, giving a
serious 3x to 5x performance improvement (e.g., compared with an
OPA637 opamp). I'd say it's well worth the trouble.

I'm planning to experiment with a PD amp using OPA637B configured
with the BF862 bootstrapping as shown in Linear's app note "Low Noise
Amplifiers for Small and Large Area Photodiodes Design Note 399".

My circuit is a bit more complex, to insure low-Z HF bootstrap
drive and provide DC PD biasing, while maintaining the 0.8nV
bf862 voltage-noise capability.

I bought some of the last remaining OPA637BPs on the planet from
Newark a few months ago. There's still a small handful of the 'A'
grade out there.

What the heck is going on with TI's Burr Brown parts manufacturing?

If you ask TI, they'll give you a straight answer: They badly
miscalculated and didn't replace Burr-Brown's automated test
sets far enough in advance to keep up with the fact the old
ones were failing and could no longer be fixed. The new ones
are in place, but the programming is going slowly. They're
bringing back the products several at a time and they hope to
have everything back by next spring. Oh, they do apologize.

.

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