64 



BELL SYSTEM TECHNICAL JOURNAL 



Plate current-plate voltage characteristics and screen current-plate 

 voltage characteristics for a power pentode of the indirectly heated 

 cathode type, are shown in Fig. 8. The secondary emission "fold" 



100 



90 



if) 80 



5 70 

 < 



d 60 



5 



.50 



^ 30 



< 



7^ 20 



10 







30 



25 



, -I/) 



z ^ 

 u °^ 20 



^^ 



3l 15 

 Z _l 



52 



10 



50 100 150 200 250 300 350 400 450 500 550 600 650 

 PLATE VOLTS, Ep 



Fig. 8 — Characteristics of a power pentode. Plate current, 7p, and screen current, 

 7„ as functions of the plate voltage with various values of the control-grid voltage, Eq, 

 as parameters. Screen voltage, E^ — 250 volts throughout. Load lines are shown 

 for resistance loads of 6000, 10,000, and 20,000 ohms. 



in the characteristics is almost completely eliminated by the suppressor 

 grid. 



The effectiveness of the suppressor grid is shown by the charac- 



