An Extension of the Theory of Three-Electrode Vacuum Tube Circuits

T HE relations between input voltage and output current of the three-electrode vacuum tube when connected to impedances in both input and output circuits have been the subject of several papers. One of the first more extensive treatments of this problem was given by J. R. Carson,1 using a method of successive approximations. The theory was further extended by F. B. Llewellyn,2 E. Peterson and H. P. Evans, 3 and J. G. Brainerd.4 The theories given by these authors did not take into account any feedback between input and output circuit except in the first approximation. The aim of the present paper is to extend the theory of the threeelectrode vacuum tube to include the effects of feedback between input and output circuits not only in the first but also in the second and higher approximations. The assumptions underlying Carson's treatment, constancy of the amplification factor and absence of conductive grid current, will be maintained. The extension of the present theory to such cases as treated by Llewellyn, Peterson-Evans and Brainerd still remains to be done. J. F. E. * J. 2 3 1