NEGATIVE-GRID VACUUM TUBES 581 



TABLE II 

 Referring to Fig. 7 

 Let CcJ, Cgp', Ccr' '"-' capacitances of cold tube, 



y = - - = ratio of g — p to c — g spaciiiJL;, 



T 



A = -=r = ratio oi g — p to c — g transit time. 



i e 



Then when h—*-0: 







Tp = same as at low frequencies, 

 r _ ^ r ' r 1 + y + MO 



1 r^ 



5 MO 



r 1 + y + MO 1 _ 

 [1+3^+..] 



'■'" ~ 80 MO 



^ _ /- /T 1 +y + MO 



that the cathode-plate and cathode-grid capacitances have dielectric 

 constants greater than unity, but that the grid-plate capacitance has 

 a dielectric constant less than unity. The cathode-grid resistance is 

 positive, and the grid-plate resistance is negative. 



The outstanding result of this investigation of the network repre- 

 senting the negative-grid tube is the demonstration of the slight 

 modification required in our conventional network to make it accurate 

 even in the ultra-high-frequency range. The amplification factor is 

 the familiar low-frequency one, and at moderately high frequencies, 

 the only alteration needed in the conventional diagram is the addition 

 of two small but very important resistances, one in the cathode-grid 

 path and one in the grid-plate path, where the resistance in the latter 

 path is negative in sign. 



Part II 



In a recent paper, ^ general equations have been derived which 

 describe the behavior of vacuum tubes at ultra-high frequencies. In 



1 Loc. cit. 



