You have to know how to calculate noise in your circuit. Why? If you don't see or measure expected signal strength at the end of a line or component then the circuit will not work. For example an antenna needs a specified power level in order to radiate to a certain distance. If you don't have expected power at there then the antenna may not work. Similarly noise calculation is also required to evaluate data transfer speed or to improve data transfer speed. You can imagine how noise effects your whole design. Therefore you need to know the different types of noise that exists and how to calculate them so that your calculation for the system design is good.

There are 3 different types or sources of noise- (1) Thermal Noise, (2) Shot Noise (3) Flicker Noise.

Thermal Noise

Types of Noise that you should know aboutAs the name explains itself, thermal noise is due to temperature. This is the usual and basic type of noise that is present in all electrical or electronics circuits. Due to the temperature or heating effect, the charges in the circuit may vibrate disturbing the information bearing signal. Thermal noise is also known as Johnson or Nyquist noise because these are the scientist who first studied it. The power spectral density of noise is usually used in communication circuit study.

See How to calculate Thermal Noise Power?

Shot Noise

Shot Noise arise due to escaping of charge across some potential barriers. For example semiconductor, diodes or thermionic devices have potential barrier that bounds charges in their respective region. But consider the situation when fluctuation of charges due to some device fabrication fault, some unexpected potential fluctuation in some of the system causes the bound charge to cross over the potential barrier. Such crossing of one or more charge causes overshoot of voltage or current which is measured as a some sort of shot. This type of unwanted signal is called shot noise.

Flicker Noise

The last type of noise is called flicker noise. This type of noise is due to variety of sources such as impurity doping level in semiconductors and other dynamics of solid state devices. This is also known as 1/f noise because its magnitude decrease with higher frequency. It is also called pink noise.


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