Abstracts of Technical Articles by Bell System Authors 



Network Analysis and Feedback Amplifier Design} H. W. Bode. The 

 material for this book was originally prepared as a text for an informal 

 course at Bell Telephone Laboratories. It is the outgrowth of a research 

 directed at the problem of designing degenerative feedback amplifiers to 

 provide substantial feedback without instability. The solution of the 

 feedback problem is, however, dependent upon certain propositions in 

 general network theor>^ which are applicable also to other situations. With 

 the addition of other logically related material, this has made the book 

 primarily a text on general network theor>^ 



Earlier texts on networks have been concerned primarily with trans- 

 mission line and filter theory. The present book emphasizes the broad- 

 band aspects of network theory. In other words, it is concerned with the 

 problem of providing characteristics which var>^ smoothly, and in some 

 prescribed manner over a broad frequency range. This aspect of network 

 theory is stressed because it is the one which best fits the feedback problem. 

 It also has applications, however, to the many broad-band problems which 

 arise in television, frequency modulation, multi-channel carrier telephone 

 and other modern communication systems. 



The emphasis on broad-band problems has a number of consequences. 

 For example, it gives special importance to networks including resistances 

 as well as reactances, since it is frequently only by the use of controlled 

 dissipation that network characteristics can be made to var>' smoothly 

 over broad ranges. The emphasis on broad-band applications also requires 

 special attention to the effects of parasitic elements, and several sections of 

 the book are devoted to the development of design methods for networks 

 including prescribed parasites. A final consequence is the importance 

 which is assumed by the limitations on the characteristics which can be 

 obtained from physical networks. Over very narrow bands only ver\' mild 

 limitations exist, but as the band becomes broader the available charac- 

 teristics become more and more restricted. 



The other principal point of emphasis of the book is on the use of net- 

 works in association with vacuum tubes, rather than as purely passive 

 structures. The primary theoretical development of the book is stated in 

 terms of general active circuits. Otherwise the effort to extend network 



' Published by D. Van Nostrand Company, Inc., New York, N. Y., 1945. 



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