OPERATION Of THERMIONIC VACUUM TUBE CIRCUITS 451 



In order to apply the general equations we must evaluate z„ and q„. 



To Evaluate z„. 



From the general equations, we have 



rp-\-Zn 

 Hence we may write Kirchoff's law for the plate circuit. This gives 



. _ gg[(M+ 1)22+^23] 



^ rpZ2-\rZ-A{rp'^Z2) ' 



Upon equating the two expressions for ip, there results 

 ^ z^ifJ-Zs — rp) 



(lJL+l)Zo-\-tiZ3' 



To Evaluate q„. 



By the general equations, we have 



e 



^g = — i 



rg-\-q„x 



where x stands for 



V V rp-\-ZnJ 

 This may be written 



X 



which says that Kirchoff's law may be applied to the grid circuit 

 provided we use a modified voltage, -, and a modified grid resistance, 

 — . Hence 



X 



e 



X ^ 



Upon equating the two expressions for ig there results 



21/ r. , \ 



qn = 



Sg K _ M 



V rp-\-Zn 



