SHOT NOISE IN DIODES 



617 



The effect of transit time on the pure shot noise for a low space 

 charge density and a high plate voltage may be obtained quite readily 

 from (57) and (58). Since for a very small space charge, Iq and Ua are 

 small, and «« large, the equations then reduce to the following ex- 

 pression : 



1 1 aaT~ Qa 



Vl = -. ;r- -\-^-aaT- 



1 



vAi^ 



+ g-'" - 1) 



(71) 



1 234 5 67 8 9 10 II 



TRANSIT ANGLE IN RADIANS 



Fig. 4 — Effect of transit time on both thermal and shot tube noise. 



'eI_ = 4.Sk(0.6UT)rpdf, 

 7/2 = leSIdf. 



For these operating conditions, the transit time in terms of the d-c. 

 acceleration and the electrode spacing is given by 



X = 



aaT^ 



In terms of the external circuit impedance Z/ 



Vl = hZf, 



(72) 



