Thermalrauschen

Thermalrauschen, also known as Johnson-Nyquist noise or Johnson noise, is a fundamental source of electronic noise present in all electrical conductors. It arises from the random thermal motion of charge carriers, typically electrons, within a conductor. These charge carriers are in constant random motion due to their thermal energy, and this agitation leads to fluctuating voltages and currents, even in the absence of any applied signal or external stimulus.

The power spectral density of thermalrauschen is uniform across all frequencies, meaning it is a white noise process. This property is described by the Nyquist theorem, which relates the noise voltage to the temperature of the conductor and its resistance. Specifically, the mean-square noise voltage is proportional to the absolute temperature (in Kelvin) and the resistance of the conductor. Higher temperatures and higher resistances result in greater thermal noise.

While thermalrauschen is an unavoidable phenomenon, its impact can be minimized by designing electronic circuits with lower resistances and operating them at lower temperatures. It is a crucial consideration in the design of sensitive electronic instruments, amplifiers, and receivers where it can limit the minimum detectable signal. Understanding and accounting for thermalrauschen is essential for achieving optimal performance in many electronic applications.