Noise and Linear Networks
P. Heymann, Matthias Rudolph · 2021
When passing through a communications circuit or in a measuring system, the input noise is modified. Bandwidth limitations convert white noise into narrowband noise. The amplitude of the noise is increased by amplifiers and decreased by attenuators. The networks add noise components that originate from their own noise. The current source feeds a certain noise current into a circuit, no matter how high its resistance is. In practice they only exist together with an internal resistance or a conductance. The power of a noise generator is varied by means of an attenuator. The temperature appears at the output of the attenuator. It is a combination of the noise generator power and the inherent noise of the attenuator.