Noise (electronics)

Noise is unwanted random or interfering variation superimposed on an electrical signal. It can arise within components, from external sources, or through interactions in a circuit.

Thermal noise: Random voltage or current fluctuations caused by thermal motion of charge carriers in a resistive element. It arises in every resistor at nonzero temperature, even without an applied signal.
Electrical signal: A time-varying voltage or current that carries information or energy through an electrical system. Noise is identified as unwanted variation relative to the signal being carried.
Noise figure: A measure of how much a device degrades the signal-to-noise ratio, commonly expressed in decibels. It compares the noise at an amplifier's output with the noise expected from an ideal device.
Electromagnetic interference: Unwanted electromagnetic energy that disrupts the operation of an electrical or electronic system. It is often an external, identifiable disturbance rather than intrinsic random noise.
Shot noise: Current fluctuations caused by the discrete arrival of charge carriers across a potential barrier. It matters when current flows through junctions and other devices with discrete charge transfer.
Frequency domain: A representation of a signal in terms of its frequency components rather than its variation over time. Noise is often characterized by how its power is distributed across frequencies.
Low-noise amplifier: An amplifier designed to add as little noise as possible while boosting a weak input signal. Its input-referred noise can determine the sensitivity of an entire receiving system.
Crosstalk: Unwanted coupling by which a signal in one circuit or channel appears in another. It creates interference from neighboring signals rather than from a circuit's own random fluctuations.
Flicker noise: Low-frequency noise whose power spectral density generally rises as frequency decreases. It often dominates electronic noise near zero frequency and in slowly varying measurements.
Bandwidth: The range of frequencies a system or signal occupies or passes. Integrated noise depends on the bandwidth admitted by a circuit or measurement.

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