Noise of an imaging front-end

[ChrisNeumi]

I'm designing an imaging front-end with a CCD Detector. Now I want to
predict, what my system SNR will be. From the optics and the detector
everything is quite clear and in my model.

How can I model the electronic readout circuit of the CCD, particularly
the AD-converter?

Does anyone have experience?

 

[Tim Wescott]

ChrisNeumi wrote:

I'm designing an imaging front-end with a CCD Detector. Now I want to
predict, what my system SNR will be. From the optics and the detector
everything is quite clear and in my model.

How can I model the electronic readout circuit of the CCD, particularly
the AD-converter?

Does anyone have experience?

How accurate a model do you want?

As a first cut you can just model the ADC as a pass-through.

Then add in uniformly distributed noise one LSB wide, to simulate
quantization.

Then note that a fast ADC like that has more "conventional" noise in
it's front end than quantization noise, so add that in as well (consult
the data sheets).

Then note that a fast ADC like that suffers from charge injection when
it converts, so add in that effect (consult data sheets, app notes, app
engineers).

If you are buffering the signal note that your buffer amplifier
generates noise -- add that in.

Oh -- your ADC has differential and integral nonlinearity -- do you
care? If yes, add it in.

Sampling? Add it in.

Etc.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com