lämpökohinasta

Lämpökohina, also known as thermal noise or Johnson-Nyquist noise, is a fundamental electronic phenomenon that occurs in all electrical conductors and semiconductors at temperatures above absolute zero. It arises from the random thermal motion of charge carriers within the material. These charge carriers, typically electrons, are constantly in motion due to their thermal energy. As they move randomly, they create fluctuating currents, which in turn generate a fluctuating voltage across the conductor.

The magnitude of thermal noise is directly proportional to the absolute temperature of the conductor and the bandwidth of the measurement. Higher temperatures lead to more vigorous thermal motion and thus stronger noise. Similarly, a wider frequency range over which the noise is observed will result in a larger total noise power. The noise power spectral density, which describes the noise power per unit frequency, is constant over a wide range of frequencies, a characteristic known as the white noise property of thermal noise.

Thermal noise is an inherent limitation in electronic circuits and is a significant factor in determining the sensitivity of measurement devices. It can mask weak signals, making it difficult to detect them accurately. Engineers often employ strategies to minimize the impact of thermal noise, such as operating at lower temperatures, using low-noise components, and employing filtering techniques to reduce the bandwidth of the signal processing. Understanding thermal noise is crucial for designing and analyzing electronic systems, especially those that deal with very small signals or require high precision.