29-11-2012, 11:14 AM
What is Thermal Noise?
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Thermal noise in the resistance of the signal source is the fundamental limit on achievable signal sensitivity
is unavoidable, and generated by the random thermal motion of charge carriers (usually electrons), inside an electrical conductor, which happens regardless of any applied voltage.
Thermal noise is approximately white, meaning that its power spectral density is nearly equal throughout the frequency spectrum.
Noise caused by thermal interaction between free electrons and vibrating ions in a conductor.
Shot Noise
Shot noise is a type of electronic noise which originates from the discrete nature of electric charge.
Shot noise is due to the random arrivals of electron packets at the potential barrier of forward biased P/N junctions.
The Shot noise is current arising from the random generation and flow of mobile charge carriers.
Dark Current Noise
dark current is the relatively small electric current that flows through photosensitive devices such as a photomultiplier tube, photodiode, or charge-coupled device even when no photons are entering the device.
It is referred to as reverse bias leakage current in non-optical devices and is present in all diodes. Physically, dark current is due to the random generation of electrons and holes within the depletion region of the device that are then swept by the high electric field.
The charge generation rate is related to specific crystallographic defects within the depletion region. Dark-current spectroscopy can be used to determine the defects present by monitoring the peaks in the dark current histogram's evolution with temperature.