TRIGGERED PULSE GENERATORS 



In view of the complications involved in correct penthouse waveform 

 generation the author has never used constant-voltage deflector coil drive. 

 Its advantage lies in its management of a quantity we have rather ignored, 

 the coil stray capacitance. The cathode follower has no difficulty in supplying 

 extra current to charge this, whilst still maintaining the correct P.D. across 

 the coil (Figure 16.35). The pentode, on the other hand, is obliged to supply a 



Ideal 



coil 

 current 



Ideal 



coil 



voltage 



Stray 



capacitance 

 current 



k 



r 



Ideal 

 total 

 current 



Figure 16.35 



triangular total current, which means that the coil current cannot itself be 

 triangular, there must be some distortion. In the author's experience, with 

 coils made with reasonable care the effect is not serious. 



REFERENCES 



1 Attree, V. H. J. sci. Instrum. 11 (1950) 43 



2 Dickinson, C. J. Electronic engineering monograph Electrophysiological Tech- 



nique p. 49 

 ^ PucKLE, O. S. Time Bases London; Chapman & Hall 

 ^ Attree, V. H. /. sci. Instrum. 26 (1949) 257 



5 GiBBS, D. F. and Rushton W. A. H. /. sci. Instrum. 23 (1946) 220 



6 Moody, N. F. and Williams F. C. J. Instn. elect. Engrs. 93 Pt IIIA, No 7 



252 



