Graphical Analysis of Output Tube Performance

After outlining the graphical method for the analysis of power tube output as applied to the case of a simple resistive load the method is extended to the case of a plate load presenting a value of resistance that is different for direct current than for alternating current. It is shown that in this case the various load lines cannot be drawn through a common operating point because the effective plate voltage shifts when rectification occurs. The method is applied to an experimental pentode and it is shown that in this case the condition for no rectification does not imply the absence of odd or even harmonics.