18 BELL SYSTEM TECHNICAL JOURNAL 



designed to make the gain-frequency characteristic of the amplifier 

 with feedback of the same shape as the loss-frequency characteristic 

 of a non-loaded telephone cable. 



Conclusion 



The feedback amplifier dealt with in this paper was developed 

 primarily with requirements in mind for a cable carrier telephone 

 system, involving many amplifiers in tandem with many telephone 

 channels passing through each amplifier. Most of the examples of 

 feedback amplifier performance have naturally been drawn from 

 amplifiers designed for this field of operation. In this field, vacuum 

 tube amplifiers normally possessing good characteristics with respect 

 to stability and freedom from distortion are made to possess super- 

 latively good characteristics by application of the feedback principle. 



However, certain types of amplifiers in which economy has been 

 secured by sacrificing performance characteristics, particularly as 

 regards distortion, can be made to possess improved characteristics 

 by the application of feedback. Discussion of these amplifiers is 

 beyond the scope of this paper. 



