How Does Shot Noise in a Photodiode Lead to White Noise Characteristics?

Click For Summary
SUMMARY

The discussion centers on the characteristics of shot noise in photodiodes, specifically how it leads to white noise behavior. The output current fluctuations in a photodiode, described by the formula d(Var(I)) = 2eI*df, indicate that these fluctuations are independent of frequency, confirming their classification as white noise. The conversation also touches on the integration of power spectral functions to derive total voltage fluctuations, referencing the Wiener-Khinchine theorem for further understanding.

PREREQUISITES
  • Understanding of photodiode operation and current generation
  • Familiarity with Poisson statistics and stochastic processes
  • Knowledge of the Wiener-Khinchine theorem
  • Basic concepts of power spectral density in signal processing
NEXT STEPS
  • Study the derivation and implications of the formula d(Var(I)) = 2eI*df
  • Research the Wiener-Khinchine theorem and its applications in noise analysis
  • Explore the characteristics of white noise in electronic devices
  • Investigate methods for measuring and analyzing shot noise in photodiodes
USEFUL FOR

Electrical engineers, physicists, and researchers focusing on noise analysis in electronic devices, particularly those working with photodiodes and signal processing.

aaaa202
Messages
1,144
Reaction score
2
Not really sure where this belongs... But here goes:
If you illuminate a photo diode it generates a current because electrons are being emitted from its cathode. Since each emission is however an independent stochastic process the output current will be subject to fluctuations, which can be described using Poisson statistics.
Now in my book a result is that for the variance of the current in a frequency interval df, is given by:
d(Var(I)) = 2eI*df
, where I is the average current measured over long times.
This formula shows that current fluctuations are true white noise, since they are independent of the frequency. However it also confuses me a bit. To obtain the total fluctuations one will have to integrate over all possible frequencies. Doing so the integral of the above will diverge. What have I misunderstood?

I would also like to understand why in general integrating over the power spectral function gives us the total voltage fluctuations. It follows from the above when the noise is shot noise, but how do you know it to be true in general?
 
Physics news on Phys.org
Read about Wiener-Khinchine theorem to figure out why integrating the power spectral density results in total fluctuation.
 

Similar threads

Graduate Calculating the variance of integrated Poisson noise on a defined quantity
  • · Replies 36 ·
2
Replies
36
Views
4K
Why is the U-2 nicknamed the Dragon Lady?
  • · Replies 4 ·
Replies
4
Views
9K