EQUIVALENT CIRCUITS OF NETWORKS 



599 



These equations are again of the form 



h = ^21 Vi + ^22 V2 



where now 



1 



(11) 



^11 = - + ^C0(C,c + C,p) 



/321 = 



+ ^coC, 



^2 



=-r- 



+ ioiiCpc + Cp) 



(12) 



The network interpretation of Fig. 5 is consistent with (10) and so does, 

 in fact, constitute a possible network representation. 

 From (12) the relation 





(13) 



is obtained. The thing to emphasize is that this sum is independent of the 

 passive feedback admittance and that it is a constant independent of fre- 

 quency within the range considered. It is, moreover, a quantity which 

 only is correlated with the conduction currents in the tube. For lack of a 

 better name the sum (13) will be referred to as "the effective transconduct- 

 ance." It will play an important role in the later discussion. 



As still higher frequencies (above 10 cps) were employed it necame neces- 

 sary to take into account lead effects, usually in the form of self and mutual 

 inductances, and by incorporating them in the network of Fig. 5 a slightly 

 more involved circuit was obtained. This more general network is still 

 determined by equations of the form (11), for adding the new network ele- 

 ments merely means that linear transformations are applied to the potentials 

 Vi and V2 with the result that a new set of jS-coefficients is obtained, the 

 new set being merely of somewhat more complicated form than the first. 



With the utilization of frequencies so high that the electron transit times 

 became comparable with the period of the applied signal, further complica- 

 tions arose and the equivalent network idea was put to a severe test. In 



