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BELL SYSTEM TECHNICAL JOURNAL 



acteristics one parameter being fixed in each case. For the dynamic 

 characteristic see section 12. Equation 2, of course, fits only the 

 portions of the curves characterized by temperature saturation. 



5 -f- -/- 



isEb-Ec-c) 2 

 Fig. 9 



JO 20 10 



10 20 30 



Grid Volts 



Fie. 10 



Anode Voltage 



Fig. 11 



The abruptness with which the curves of Fig. 10 meet the potential 

 axis is important in certain uses to which tubes are put. The value 

 of E g which reduces I p to zero is called the cutoff voltage. To have a 

 sharp cutoff a tube should have a fairly large fx and its grid should be 

 sufficiently large with respect to the filament to effectively screen all 

 parts of the filament from the plate. 



