Re: High speed photodiode amp

On Sat, 13 Jan 2007 00:45:48 +0100, Rene Tschaggelar <none@xxxxxxxx>
wrote:

Robert Scott wrote:

I need to make a detector that can register rise times as small as 10
microseconds for display on an O-scope. I do not need sensitivity (the source
is a CO2 laser - optically attenuated as needed). I do not need DC stability.
I do not need linear gain. I am only interested in using this detector to
verify the rise/fall time of the laser light. I have seen various op-amp
transconductance amp circuits, but they would require an exotic op-amp to
achieve the bandwidth. I am hoping that all the things I don't care about will
allow the use of something simpler - like a single bipolar transitor?


Robert,
contrary to what others tell, you'll have aproblem.
The speed is not high speed, rather low speed, at
least what we're usually used to. No, your problem
is the source. CO2 at 10um requires a sensor that
is sensitive in that range. Silicon isn't. Germanium
isn't. A thermopile is, but has nowwhere the
required bandwidth. Possibly a LN2 cooled CdHg
something.

Rene


10 microns? That's practically RF!

John

.

Relevant Pages

  • Re: High speed photodiode amp
    ... I do not need sensitivity (the source ... is a CO2 laser - optically attenuated as needed). ... but they would require an exotic op-amp to ... required bandwidth. ...
    (sci.electronics.design)
  • Re: High speed photodiode amp
    ... microseconds for display on an O-scope. ... I do not need sensitivity (the source ... is a CO2 laser - optically attenuated as needed). ... but they would require an exotic op-amp to ...
    (sci.electronics.design)
  • Re: High speed photodiode amp
    ... Robert Scott wrote: ... I do not need sensitivity (the source ... is a CO2 laser - optically attenuated as needed). ... It may help to put a resistor in parallel with the photodiode to keep some current flowing through the transistor -- this keeps the speed up when going back to the no-light condition, but gives you some work to do with the offset voltages. ...
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  • Re: High speed photodiode amp
    ... 10 microseconds for display on an O-scope. ... sensitivity (the source is a CO2 laser - optically attenuated as ... op-amp to achieve the bandwidth. ... If you really don't need sensitivity, ...
    (sci.electronics.design)