Summary: I am stuck with the measurement of shot-noise-intercept-current of PDA255. Seeking help.
Motivation: It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector.
Method: It is as described in the elog 7907
Result: The plot is attached here.
Discussion: The result I got is really unexpected, the noise voltage should increase with the DC current level that corresponds to the increment of light level too. But actually it is decreasing. Three times I have repeated this experiment and got the same result. I want some suggestion on this regard.