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BELL SYSTEM TECHNICAL JOURNAL 



those for the power pentode shown in Fig. 12. For the co-planar-grid 

 tube, as for the pentode, the third Harmonic is comparatively high and 

 increases with the load resistance, while the second harmonic curves 

 exhibit minima. This is to be expected from the form of the dynamic 

 characteristic which is very similar to that of similar curves for the 

 pentode previously discussed. For example, consider the curves 

 marked 2 in Fig. 20, obtained with Ep = 130 volts, £„ = 75 volts and 



70 



60 



CO 



y 50 

 a. 



2 40 



Z 



30 



20 



10 



-110 -100 -90 -80 -70 



-60 



-50 -40 -30 

 GRID VOLT AGE. E, 



-20 -10 



10 



20 30 



Fig. 21 — Plate current-grid voltage characteristics of a triode with a dynamic char- 

 acteristic shown for a resistance load, R = Rp = 1140 ohms. 



Eg = — 60 volts. The output power under these conditions, with an 

 input of 50 peak volts, is 1.68 watts with the second and third har- 

 monics 40 db and 25 db, respectively, below the fundamental. At an 

 input of 30 peak volts, the level of the second harmonic rises to 29 db 

 and that of the third harmonic falls to 41 db below that of the funda- 

 mental. 



