Re: About TIAs

On a sunny day (Fri, 27 Dec 2024 14:14:31 -0000 (UTC)) it happened Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote in
<vkmco7$3l6df$1@dont-email.me>:

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).
 

>
That’s basically a homebrew phototransistor, and may work great for
applications that don’t require high speed, low noise, or accurate
calibration. (There are lots of those.)
>
A slightly more advanced method is to replace the NPN with a cheap MMIC
amplifier. If you have at least a milliamp of photocurrent, that’ll get you
close to the shot noise, and it’ll be pretty fast unless the PD itself is
slow.
>
We sell fancier photoreceivers for much dimmer light, where it’s more
difficult to preserve both low noise and wide bandwidth.

Yes
I was stunned a while back when I looked at the circuit diagram of my 5 dollar satellite LNB
 https://panteltje.nl/pub/5_dollar_LNB_PCB_IMG_3582.GIF
About 11.7 GHz center frequency.. 10.7 to 12.7 GHz range.
One cavity,, one small rod (part of wavelength) one base resistor and one RF transistor:
 https://www.nxp.com/docs/en/application-note/AN11698.pdf
  see figure 6
They use the base resistor to switch between a horizontal and vertical positioned (receive polarity) rod.
Of course much is in the layout, but the idea is cool, should work
just as well with a photo diode of sorts?


Noise is incredible low, my 5 dollar LNB (and others) in use now for almost 25 years
in the cold, in the hot days, in lightning.. in rain...
I have modified some LNBs local oscillators (for the down-mixer crystal)
locked to my Rubidium reference.
all works fine.

It all depends on what you mean by bandwidth, from a RF POV
10 GHz center frequency and a few GHz bandwidth seems to work.
DC should work too :-)
Depending on the tuned PCB strips..

So nice, just a base resistor to switch, no opamps, no feedback, no delays..
no oscillations, no stop resistors to prevent oscillations.
100 % efficiency, receives radio and TV from thousands of miles away satellites.