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BELL SYSTEM TECHNICAL JOURNAL 



tion in analytical terms. The transition rests upon the physical fact that the 

 total current entering or leaving an electrode is the sum of conduction and 



Fig. 5 — Equivalent circuit of a positive grid triode at moderately low frequencies. 



Fig, 6 — Parasitic triode network. 



displacement current. The network for the displacement currents is passive 

 and is shown on Fig. 6. For this network: 



(8) 



/2 = -/3l'2Fi + i822F2 J 



where /i is input and I2 the output displacement current. The coefficients 

 appearing have the values 



^n = -io^C,^ \ (9) 



^22 = -ico(Cpc + Cg^ J 



The potentials appearing in (8) are the same as those which occur in the 

 conduction current equations (5), this being the physical condition which 

 also must be satisfied. By adding (5) and (8) and by letting /i and h 

 mean total currents we get: 



/i = fl + ia,(C,e 4- CgS\ V,-\^ + ice C,pj F2 



(10) 



