588 



BELL SYSTEM TECHNICAL JOURNAL 



is fully loaded at an output of .04-. 05 watt, representing the point 

 where the grid of a tube begins to draw current and the third har- 

 monic increases rapidly. It will be noted from the gain-load curve 

 that the output has to increase to .1 watt before there is a noticeable 

 falling off in the gain of the anij)lifier. 



For the amplifier No. 1 under the condition of 350 volt plate supply 

 the curves and oscillograms shown in Figs. 7 and 12 are of the same 



> 



130 WATT5 



I.3& WATTS 



1.71 VVATT^ ^*'"^ 



Input Voltage- 



Fig. 15 — Amplifier No. 4; 1,000 c.p.s. ; load 4,000 ohms resistance 



general nature. On account of the higher plate and grid biasing 

 potentials an output of 0.7 watts is reached before the increase of 

 third harmonic due to grid modulation occurs. This point is very 

 definitely marked in the oscillograms for, of the pictures taken at 

 outputs of 0.68 and 0.86 watts, the first is entirely free from this dis- 

 tortion, while the second where the current output is only 12.5% 

 higher shows it clearly in the flattening at the top of the curve . On 



