THE OPERATION OF VACUUM TUBES 



49 



the screen grid chnamic curves is shown. The effect is seen to be 

 similar to that for the three-element tube, though somewhat more 

 pronounced. 



40 L> 



300 400 500 



PEAK EXCITING VOLTAGE 



Fig. 16 — Dynamic output and efficiency of a screen grid tube compared to that of 

 a three-element tube. £;, = 3000 volts, Ec at cut-off Zo = 1500 ohms. 



