Fluctuation Noise in Thermionic Valves

Abstract

IN a recent paper¹, I put forward the theory that the noise generated by a thermionic valve is alternatively (a) of the shot noise type if the valve anode current is temperature-limited, or (b) of the thermal or ‘Johnson noise’ type if the current is fully space-charge limited. (Contrast Llewellyn's theory that the noise in the presence of space-charge is the sum of shot and thermal noise, with a smoothing factor applied to the shot noise.) In the paper quoted, however, there was no quantitative treatment of the practical case of a valve which is partially spacecharge limited, that is, does not correspond exactly to either of the simple states of temperature or space-charge limitation.