OPERATION OF THERMIONIC VACUUM TUBE CIRCUITS 455 



Explanation: 

 I=KE' 

 = K{M+A cos pt)-]K+ 



= 2^+ii cos pt+b-2 cos 2 pt+ ... 



3.0 

 2.6 

 Z.(i> 

 2.4 

 2.2 

 2.0 

 1.8 

 1.G 

 1.4 

 1.2 

 1.0 



, 2KA^r3 . 1 1 



Oi = I 2.^ina— acosa+-- sni 3a I 



P\ni(lamcntal current is: 



tf = b\ cos /)/. 



Then 



e /I cos M A 



r = - 



b\ cos pt b\ 



and 

 Factor = 



^E 



Ai 



Hence the resistance to pure sine wave of square-law 

 devices in the vicinity of cut-ofT is 



A/ 



X Factor. 



Dotted curves show factor for modulated waves of the 

 form A{l-\-B cos qt) cos pt where 



^E = 2Ai\^-B). 



FRACTION OF 2A DURING WHICH CURRENT FLOWS (A) 



Fig. 7 — Correction factor for resistance of non-linear device 



while the other is introduced into the grid circuit. To analyze this 

 condition for the general case, (see Fig. 8) let lower case e's refer to 

 the driving voltage impressed directly on the grid. Let the £'s refer 

 to the driving voltage in series with an impedance in the plate circuit. 

 We then have the series 



ip=ai{E^e)+a.{E+eY+ . . . 



