EQUIVALENT CIRCUITS OF NETWORKS 



603 



In regard to the general network of Fig. 8 it may be noted that the 

 network is composed of two parts. One part obeys the reciprocal law and is 

 represented by a 11 (or T) network and is consequently specified by three 

 parameters. The other part is merely an impressed current controlled by 

 the input potential Vi . From the fact that the 11 (or T) network obeys the 



|vi Cgc 



gp 



■(^<)M 



T^(-.)f ^p-^ 



Cpc |V2 



1- 



Fig. 9 — Equivalent circuit of a positive grid triode at moderately low frequencies; 

 current impressed at the output. 



|(/3<2+/32,)V2 



I^' 



y3; 



(y3ii-/32l) -(/322+/32i) 



}v. 



Fig, 10 — Equivalent circuit of an active four-pole; current impressed at the input. 



t-(t^^) 



Fig. 11 — ^Equivalent circuit of a positive grid triode at moderately low frequencies; 

 current impressed at the input. 



reciprocal law, the conclusion does not follow that it in general behaves as a 

 passive network. The element values may, for example, be negative, and 

 Bode's integral relations may not necessarily be true for this network. 



It should further be noted that the network representation holds for all 

 frequencies. The effect of frequency will be that the admittances in the 

 network change and in changing they will, for example, reflect effects due to 

 parasitics and electron transit time. 



