OPERATION OF THERMIONIC VACUUM TUBE CIRCUIT."^ 443 



Since amplifiers are usually operated under the condition that rg 

 is exceedingly large, the general solution has contributed nothing 

 new to the amplifier equations for conditions where the grid is main- 

 tained at a negative potential with respect to the filament. But for 

 positive values of grid potential both g/, and the reflex factor, v, enter 

 into the calculations. It may be remarked in passing that when 

 the grid and plate are both positive by the same amount, the absolute 

 value of V is approximately equal to, or somewhat less than, ix. On 

 the other hand, when, as is usually the case, the plate potential is 

 much greater than the positive grid potential, the magnitude of v is 

 much greater than fx. 



Ep, Volts 



E„ Volts 



Fig. 2 — Change of /x with plate and grid potentials. The points on the calculated 

 curve were obtained as follows: since 



then 



where 



K = 



From the upper curve, for £^ = 120, Eg = —2.5 



M = 32, ;|^ =.05328, 



oEp 



whence 



if = .06146,;:i„ = 29.55 



We next consider the component of (31) that results in plate curva- 

 ture detection or modulation. It is given by 



