Notes on the Theory of the Single Stage Amplifier

The theory of the single stage vacuum tube amplifier is generalized and also extended to include phenomena of interest in vacuum tube and receiver design at high frequencies. General expressions are derived for the increase in the input admittance due to feedback, for the conditions for stability, and for the gain, as functions of the various parameters of the tube and the associated circuits. These expressions are then examined in some detail. Two specific results of especial interest are given: the case of feedback through a parallel path of susceptance and conductance, and the conditions which result when the transfer admittance consists not only of a real part but also of an imaginary part.