Reliable electronic circuit design must account for the parameter variations over the normal life of components to insure satisfactory operation. An analytical design method is derived for an Eccles-Jordan triode flip-flop in which the “worst” condition of voltage and component tolerances conditions are assumed that assures satisfactory operation for normal conditions. The method of analysis is to divide the flip-flop circuit into separate parts, write appropriate equations, and solve them simultaneously. The design method results in the best configurations of component values, regardless of what tube may be used, and actually specifies characteristics which-the tube should have, as well as the expected life of the tube in terms of maximum plate resistance.