A new simple technique for 2-terminal negative resistance cireait analysis and synthesis is developed, by using the equivalent e.m.f. defined as a function of input lotage or current variation. The technique is applied to design 2-terminal junction transistor negative resistance circuits based on the parameter control method. Modeling circuits for SCR, GTO-SCR and SSS are also derived from the proposed transistor negative resistance circuits, and the merits of the modeling circuits are discussed.