Triode cathode-followers: A graphical analysis for audio frequencies

Graphical methods are presented with which one may determine the operating path upon the plate-current characteristic curves for several commonly used feedback circuits. These include the ordinary RC-coupled triode stage without a cathode bypass capacitor and two forms of the cathode follower: one in which the grid is returned to ground, the other in which it is returned to a tap on the cathode bias resistor. Once the operating path is established, the familiar computations which determine the gain, the 2nd and 3rd harmonic distortion, the dissipated and delivered power, etc. for the common triode stage may be used here. Excellent agreement is found between predicted and measured results.