Noise is generated wherever electrons move in an uncoordinated manner, i.e. in all conductors, passive and active components and electronic circuits. These temperature-related electron movements are statistically distributed and cause the noise generated by all components themselves, the inherent noise.
The inherent noise impairs signal transmissionand must not exceed the signal level, otherwise the signal is lost in the noise and can no longer be separated from it. It is specified in decibels( dB). In order to be able to determine the relationship between the signal level and the inherent noise exactly, the inherent noise is related to the input or the output of amplifiers or other quadripoles and specified as equivalent input noise or equivalent output noise. It is particularly important to note for high- sensitivity signal amplifiers, RF amplifiers, antenna amplifiers, mixers, operational amplifiers, microphone preamplifiers, and other components.