Thermal noise, also known as Johnson-Nyquist noise, is the random electrical noise generated by the thermal agitation of charge carriers in a conductor at equilibrium. It is an unavoidable phenomenon that sets a fundamental limit on the sensitivity of electronic devices and is characterized by a Gaussian distribution with a power spectral density proportional to temperature and resistance.

Thermal Noise

Thermal noise

Johnson-Nyquist Noise, also known as thermal noise, is the electronic noise generated by the thermal agitation of charge carriers (typically electrons) inside an electrical conductor at equilibrium, regardless of any applied voltage. It arises from the fundamental principles of thermodynamics and is unavoidable, affecting all resistive components regardless of their composition.

Johnson-Nyquist noise

random electrical noise

Thermal agitation refers to the random motion of particles within a material due to thermal energy, which increases with temperature. This microscopic movement is integral to understanding thermal properties and behaviors such as diffusion, heat capacity, and conductivity of materials.

thermal agitation

Charge carriers are particles or quasiparticles that carry electric charge, essential for the conduction of electricity in materials. In conductors, charge carriers are typically electrons, while in semiconductors, they can be electrons or holes, and in electrolytes, they are ions.

charge carriers

conductor at equilibrium

unavoidable phenomenon

sensitivity of electronic devices

The Gaussian distribution, also known as the normal distribution, is a continuous probability distribution characterized by its bell-shaped curve, where the mean, median, and mode are equal, and it is defined by its mean and standard deviation. It is fundamental in statistics and natural sciences due to the Central Limit Theorem, which states that the distribution of the sum of a large number of independent, identically distributed variables tends towards a Gaussian distribution, regardless of the original distribution of the variables.

Gaussian distribution

Power spectral density (PSD) is a measure of a signal's power intensity in the frequency domain, providing insights into how power is distributed across different frequency components. It is essential for analyzing signals in various fields like telecommunications, audio processing, and vibration analysis, helping to identify dominant frequencies and noise levels.

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