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BELL SYSTEM TECHNICAL JOURNAL 



cut off during the rest of the cycle, as illustrated by Fig. 4A. Also, 

 instead of being a pure resistance, the output circuit consists of a tuned 

 tank circuit, Fig. 3>, into which resistance is introduced either directly 

 or by coupling in some way. Thus the impedance of the output cir- 

 cuit will be a resistance to the fundamental frequency only. How- 

 ever, the same general principles will apply in this case as in the case 



..| 



Lb 



I — "Mmm^ 



Eb 



IF 



1 



^ zo 



Fig. 3 — Schematic of amplifier plate circuit with tuned output impedance. 



of the sinusoidal plate current and the pure resistance circuit. The 

 equations will be of the same form except that Zq must be substituted 

 for jRo as follows : 



Eb = ipRp + iaZo, (lA) 



(2A) 

 (3) 



= Eb — i^Zq, 



U 



■ip — h, 



lb = Average of ip over 1 cycle. 



(4) 



In this case it must be remembered that the wave of ip, and hence ^'o, 

 instead of being a simple sine wave, is a more complex wave consisting 

 of a fundamental frequency and numerous harmonics. Also ioZo is 

 the sum of all such components multiplied by the respective impedances 

 presented to them taken in their proper phases. 



Considering the wave form of io shown in Fig. 4B, which is readily 

 obtainable in practice, it should be evident from inspection that it can 

 be considered a cosine wave containing odd and even cosine terms and 

 may be expressed by 



«o = /] cos w/ -\- h cos 2b)t + /s cos Swt -\- h cos 4co/ -f . . . 



-f /„ cos rnj^t. 



