Coexistent thermal and thermionic fluctuations in complex networks

This paper is concerned with the fluctuations generated in networks with non-uniform temperature distribution. Experiments are described which verify a formula relating to thermal fluctuations deduced in an earlier paper. The simplified representation adopted in that paper is fully substantiated: the fluctuations are shown to be independent of the temperature of reactive circuit elements. Coexistent thermal and thermionic fluctuations are then discussed. They are assumed to be mutually independent, and experiments are described which verify this hypothesis. A representation of thermionic fluctuations is proposed analogous to that adopted for thermal fluctuations, and a general formula applicable to certain classes of networks containing thermionic valves is deduced. This formula is applied in a concluding section to a wideband photocell amplifier. Various practical recommendations are made which yield improved signal/noise ratios.