How to design a photodiode circuit to get its dark current as output?

[anushaas]

Which is the device which will consume that current and at what voltage range?
The diode connected in reverse will not act as costant current regulator. It is not made for that purpose. Leakage current is an undesired phenomenon depend upon tepmerature and material properties. If i ask you, are you making a noise generator t hen that would be true. Diode reverse leakage is used to input an amplifier to generate noise.
See noise geneator schmatics.

Zener diodes make more noise so they are used . And see why metal oxide resistors are made and used instead of carbon resistors.
Reverse leakage current - Wikipedia, the free encyclopedia

I need to give this pA current to an electrometer circuit so as to convert it to a measurable voltage range.
Also suitable care need to be taken to eliminate the noise.

---------- Post added at 02:11 ---------- Previous post was at 02:07 ----------

Hi,
If you see carefully the data sheet shows shows the DARK CURRENT at the specified diode voltage.
View attachment 61434
View attachment 61436

True.
I need a some 10pA and hence has given a voltage source of 10V

 

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[anushaas]

I can;t know for sure, but I think he's trying to make a compensation circuit for another photodiode. Then he could substract dark current signal from useful signal. Well, that is if the dark current is exactly the same amongst all of the diodes of he same type.

Hai

Can you please tell me how to design a compensation circuit for a photodiode using another photodiode so that the noise generated in both these circuits cancel out to give a steady output dark current.

 

[FvM]

Designing a noise cancellation circuit comes next after a perpetual motion machine. By nature, noise is a pure random process, uncorrelated with a second noise signal. So it can hardly be cancelled.

 

[ALERTLINKS]

For a particular band, noise can be reduced by a log relationship, if many stages are paralelled. This is used in low noise preamplifier stage for microphone. As noise is random but to laws of probability is there. So posibility of noise signal be there in a stage and other stage are different. When many stages are in paralell, the chances of noise in all stages, in phase is less.If it is out of phase, it will cancel.
If many sources of current are in paralell, the noice will be lowered.

 

[FvM]

For a particular band, noise can be reduced by a log relationship, if many stages are paralelled.

You're referring to amplifier voltage noise and a method to reduce it (possibly increasing current noise at the same time).

The discussion is about noise current of a photodiode, which is mainly pure shot noise (due to the statistical fluctuation of charge carriers). Shot noise is also the lower bound for achievable diode current noise. In other words, there's no means to reduce it below this number.

See: Shot noise - Wikipedia, the free encyclopedia

 

[ALERTLINKS]

If i had to do such an experiment, i'll arange the system with zero current input and see practically for the noise levels and try to reduce if its too much. If i get stable output for zero input current, only then i'll go for input current source.
I expect its dc current source and taken from dark current of a photo diode. I wonder if shot noise due to photons to be considered as there are no photons in dark.

Dark current
The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the saturation current of the semiconductor junction. Dark current must be accounted for by calibration if a photodiode is used to make an accurate optical power measurement, and it is also a source of noise when a photodiode is used in an optical communication system.

 

[FvM]

I wonder if shot noise due to photons to be considered as there are no photons in dark.

The electrons forming the dark current don't care, if they have been released in the junction by photons or other processes. At best, they are completely uncorrelated and their noise density equals the known shot noise numbers. As a worse case, they may be partly correlated, resulting in a noise density above shot noise level.