1110 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



collection of electrons of high initial velocity by the control grid. Such 

 grid currents contribute to the noise, cause input loading, and may also 

 cause excessive signal distortion. 



Since h increases as the screen voltage Ec2 is increased, the figure of merit 

 likewise increases. It is desirable to keep £c2 as low as possible for at least 

 three reasons. The most important is that high screen voltage will generally 

 have an adverse effect on tube life. The second is that low power consump- 

 tion is desirable for economic reasons and the third is that it helps from 

 the standpoint of maintaining low temperatures of the components in an 



2 3 4 5 6 7 



GRID-TO-CATHODE SPACING "a" IN CENTIMETERS 



Fig. 6 — Screen voltage vs. grid-to-cathode spacing. 



9X10"3 



amplifier. Figures 6 and 7 show how Eci depends on "a" and 

 requirement that £^2 be kept low means that the range of ''o' 

 which can be used is restricted. 



'V\ 



The 



"6" 



2.3 Phase Shift 



The effects of electron transit time and lead inductance in the tubes 

 must be taken into account in order to meet the amplifier requirements 

 with respect to phase margin. In order to maintain stable operation over 



