FEEDBACK AMPLIFIER DESIGN 



449 



Fig. 21 — Frequency interval between prescribed reactances of opposite sign in a 

 resonant circuit with fixed inductance. 



oj the hand in cycles and is independent of the location of the band in the 

 frequency spectrum. 



These relations are exemplified by the plots of a low-pass cutofif 

 characteristic and the equivalent band-pass characteristic shown by 

 Fig. 22. The equality of corresponding frequency intervals is indi- 

 cated by the horizontal lines A , B and C. 



Fig. 22 — Diagram to illustrate the conservation of band width in the low-pass 

 to band-pass transformation with fixed parasitic elements. A, B and C represent 

 typical corresponding intervals of equal breadth. 



Example 



An example showing the application of the method in an actual de- 

 sign is furnished by Fig. 23. The structure is a feedback amplifier 

 intended to serve as a repeater in a 72-ohm coaxial line.^^ The useful 

 frequency range extends from 60 to 2,000 kc. Coupling to the line is 



^ The author's personal contact with this amplifier was limited to the evolution of 

 a paper schematic for the high frequency design. The other aspects of the problem 

 are the work of Messrs. K. C. Black, J. M. West and C. H. Elmendorf. 



