818 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



C between zero and 0.6. Thus the value Pm/Pio in the majority of cases 

 ^^•here the transistor is not potentially unstable is a close approximation 

 to the maximum available gain. 



The optimum source and load impedances can be expressed in terms 

 of the transistor parameters and other quantities given in terms of them 

 by the following relationships where the transistor is not potentially 

 unstable. 



G 



1 



irg i — hnhn) = e 



je 



Zs opt = Zin = hn 



hnh 



21 



CKgG^ 



Zh'>'>r 



Yl opt = —ho-z + 



2h 



22r 



1 



CKgG 



2 



(4)^ 



(5) 



(6) 



Though explicit relationships for ideal terminations and for the maxi- 

 mum power gain which one can achieve with a transistor are of interest, 

 such terminations limit the band width of the amplifiers. Therefore, it 

 is important to have convenient means for evaluating power gain and 

 input impedance for other than ideal terminations in order to realize a 

 desired bandwidth. A chart which facilitates computation of these quan- 

 tities is now developed from an analysis which leads to the other results 

 quoted above. 



Kf 



0.2 



0.4 



0.6 



c 



0.6 



1.0 



1.2 



Fig. 3 — K^ plotiod ms a f unci ion of C. 



^ If —hxih^i \s c + jd, then d = tau~'(r//c) ; G = c' and —hvihn is the conjugate 

 of —hiohii . 



