On the Flicker Noise Generated in an Interface Layer

Abstract

It is shown that a large amount of flicker noise is generated in tubes that have developed a high-resistance interface layer between the cathode-nickel and the oxide coating. The equivalent noise resistance Rn of this effect can be represented by the equation Rn=KIp2Ri2/fα, where K is a constant, Ip the plate current, Ri the interface resistance, and f the frequency whereas α varies between 1.1 (for low Ri) and 1.5 (for high Ri). All evidence suggests that the noise is generated in the interface layer; this was subsequently proved by a direct experiment. The current dependence suggests that the noise is caused by spontaneous fluctuations in the resistance Ri. Experiments up to 1.5 mc indicate a change in the exponent α from 1.1 to 1.6 at high frequencies, indicating that the interface impedance cannot be represented by a fixed resistance Ri and a fixed capacitance Ci in parallel.