lämpökohinaan

Lämpökohina, also known as thermal noise or Johnson-Nyquist noise, is a fundamental type of random electrical noise that occurs in electronic conductors due to the thermal agitation of charge carriers. This agitation causes random movements of electrons within the conductor, leading to fluctuating voltages and currents. The phenomenon is present in all conductive materials at temperatures above absolute zero.

The magnitude of thermal noise is directly proportional to the temperature of the conductor and the bandwidth of the measurement system. It is also dependent on the resistance of the conductor. Higher temperatures, wider bandwidths, and greater resistance all contribute to increased thermal noise. This noise is inherently unpredictable and cannot be eliminated, although its effects can be minimized through careful circuit design and filtering.

Thermal noise is a significant factor in the performance of electronic devices, particularly in applications requiring high sensitivity, such as radio receivers, sensitive amplifiers, and scientific instrumentation. It sets a fundamental limit on the smallest signals that can be detected. Understanding and accounting for thermal noise is crucial for engineers designing and analyzing electronic circuits to ensure optimal performance and signal integrity. The noise is often characterized by its power spectral density, which is constant across a wide range of frequencies, hence the term "white noise" when considering its frequency distribution.