What Are the Different Sources and Types of Noise?

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Discussion Overview

The discussion revolves around the concept of noise in signals, particularly in the context of electronics and signal processing. Participants explore the origins of noise, its various types, and their characteristics, including thermal noise, shot noise, and 1/f noise. The conversation includes both theoretical and practical aspects of noise, as well as references to resources for further study.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks clarification on the definition of noise and its sources, noting different types such as shot noise and thermal noise.
  • Another participant describes noise as a random disturbance represented by a Gaussian distribution, mentioning various causes and suggesting textbooks for further reading.
  • A different viewpoint emphasizes that some signal corruption is due to interference rather than random noise, distinguishing between types of noise.
  • Thermal noise is identified as a dominant source, linked to temperature fluctuations, while shot noise relates to the discrete nature of charge transport.
  • 1/f noise is discussed as having a specific spectral shape and is attributed to two-level fluctuators, with a mention of quantum noise being generally negligible.
  • Participants express differing opinions on the characterization of switching noise, with some arguing it does not conform to Gaussian distribution and others noting its relation to 1/f noise.
  • One participant encourages constructive contributions to the discussion rather than disagreements, reflecting on the nature of forum interactions.

Areas of Agreement / Disagreement

Participants express a range of views on the definition and types of noise, with some agreeing on the basic concepts while others challenge specific characterizations. The discussion remains unresolved regarding the precise definitions and relationships between different types of noise.

Contextual Notes

Some statements about noise types and their characteristics depend on specific contexts and definitions, which are not universally agreed upon. The discussion includes references to mathematical representations and assumptions that may not be fully explored.

dionysian
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Can someone please explain to me or preferibly point me torwards a resource that will explain what is ment by noise? I know that it s some kind of unwanted disturbance in a signal and that we want to get rid of it, but where does it come from. when i search online about this i find a myrid of ways of how to filter out "noise" but where does it come from?
I also noticed that there is diffrent types of noise: Shot noise, Thermal noise, burst noise... are these types of noise related or are they all diffrent phenomenoms all together?
 
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Noise is as you said, unwanted disturbance in the signal. Noise is random and mathematically it is represented by a Gaussian distribution. There are various causes of noise, some of which you mentioned. The noise from each particular source is added up and the result is in the unit of mV. This can be +ve or -ve mV and is added to the calculation done without noise (used superposition here)

Gray and Meyer is a standard textbook, but it's hard to read. If you are well versed with electronics and math then I suggest you buy the book. Another book is Mohammed Gausi (spelling?) or try Sedra and Smith (don't know if they have a chapter on noise)

Or you can just google it: http://en.wikipedia.org/wiki/Electronic_noise
 
Depends on what you mean by "noise". Unplebeian is right in that it is a "unwanted disturbance in the signal". However, much of the time the signal is corrupted due to interference (e.g. 50/60 Hz, mobile phones etc) which strictly speaking is not noise since it is not random.
There are essentially 3 types of noise: The dominant source is usually thermal noise which is due to the temperature induced random fluctuations (i.e. it scales with temperature, which is why e.g. sensitive detectors are often cooled to low temperature). Shot noise is due to the discret nature of charge transport, i.e instead of a "stream" of electrons carrying a current you get something similar to hail, the "arrival time" of the charges is randomly distributed in time. Shot noise is a problem in e.g. GaAs transistors where it tends do dominate at low frequencies.
Finally there is 1/f noise which gets its name because of the shape of the spectrum (it scales as 1/frequency). There are many sources of 1/f noise but it in general it is due to "telegraph noise" (noise sources descibed by the telegraph equation); essentially two-level fluctuators that jump back and forth.
There is also quantum noise, but that can be ignored in almost all applications.
 
Thank you both for your responses you have answered my question. I will continue to study this, just want to know the big picture.
 
unplebeian said:
Noise is random and mathematically it is represented by a Gaussian distribution.
No true, for instance, in the case of switching noise.
 
Gokul43201 said:
No true, for instance, in the case of switching noise.

Yes, that is different, but he was not talking about common mode or differential noise in the case of switching power supplies.

But it's good that you added those.
 
unplebeian said:
Yes, that is different, but he was not talking about common mode or differential noise in the case of switching power supplies.

But it's good that you added those.

Switching noise is just another name for the 1/f noise I mentioned above, it is a type of "intrinsic" noise. As the name imples the distribution is 1/f is frequency. In the time domain you get a number of "plateus" (i.e. the distribution is a set of sharp peaks, it is no where near gaussian) which corresponds to different configurations oftrapped charge (or whatever it is that is "jumping", it can also be e.g. flux).
When doing sensitive measurements it is sometimes possible to see a single particle swiching between two states, in which case the distribution consists of two peaks.
The switching can be slow; in some cases the time scale is of the order of minutes.
 
True, true. What I meant earlier is to try to add to the information that will help the origial post instead of fighting/arguing between posts by two people.

I'm sorry, but I've seen a lot of that lately on the forums (not geared towards you)
 

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