The role of current fluctuations in the control circuit of the active element in a Thompson oscillator

The effect of current fluctuations in the control circuit of the active element of a Thompson oscillator on the spectral density of amplitude and frequency fluctuations is analyzed. The standard formalism of the theory of noisy four-terminal networks is used to describe the active-element noise. A formula is obtained for determining the minimum width of the Thompson-oscillator line with two noise sources at the 'input'; and this formula is related to the noise temperature of the active element. It is shown that it is erroneous to neglect the grid current in calculating the minimum line width.