Re: About TIAs

On Fri, 27 Dec 2024 16:51:00 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

john larkin <JL@gct.com> wrote:

On Fri, 27 Dec 2024 13:45:15 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
 

https://www.electronicdesign.com/technologies/analog/article/55250719/phlux-technology-tailoring-the-design-of-transimpedance-amplifiers-to-infrared-sensor-apps-part-2
 
I just drive the photo diode directly into the base of an NPN .....
(ducks).

 
I just drive it into the emitter of an NPN. That's my Tough TIA
circuit.
 
 

>
Also a strong choice if you’ve got at least a few microamps of
photocurrent. Biasing the CB stage with a quiet current source is a win for
slightly faster things.
>
Then if your photons are valuable, you can get into closed-loop
bootstrapped bootstraps and fancy stuff like that, and wind up with
something like our
QL01 (10M ohms, 7 sq mm, 1 MHz, shot noise limited above 25 nA in the full
BW) or its just-introduced little brother the
QL03 (1M ohms, 700 kHz, 150 sq mm, shot noise limited above 60 nA).
>
Cheers
>
Phil Hobbs

No photons here: the Tough TIA is for a capacitive tank level
measurement system. The signal is a KHz-range sine wave, and we use a
synchronous detector, and tank levels don't change very fast, so
there's no big s/n problem. But the signal might be coming in over a
couple hundred feet of cable, and might accidentally get connected to
120 VAC.