lämpökohinaa

Lämpökohina, also known as thermal noise or Johnson-Nyquist noise, is a fundamental type of random electrical noise that occurs in electronic circuits and conductors due to the random thermal motion of charge carriers. This motion, caused by the temperature of the material, leads to fluctuations in voltage and current. Even in the absence of any external signal, these inherent fluctuations generate a noise signal.

The magnitude of thermal noise is directly proportional to the absolute temperature of the conductor and the bandwidth of the measurement. It is also dependent on the resistance of the conductor. A higher temperature or a wider bandwidth will result in more significant thermal noise. The noise voltage can be characterized by its power spectral density, which is constant across a wide range of frequencies.

Thermal noise is a ubiquitous phenomenon in electronics and must be accounted for in the design of sensitive instruments and communication systems. While it can limit the signal-to-noise ratio and performance of electronic devices, understanding its properties allows engineers to mitigate its effects through careful circuit design, filtering, and temperature control. It is a fundamental limit on the detection of weak signals.