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THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



sentative of the type A transistor in September, 1949. It is apparent that 

 the circuit user of" type A units had approximately a 50 per cent chance 

 of obtaining a short-circuit unstable unit from a large family of type A 

 units. The smaller shaded rectangle bounds the values of a and Vb now 

 realized in the M1729 transistor presently under development. Not only 

 has the spread in characteristics been greatly reduced as shown, but also 

 the design centers have been moved to a region for which all members 

 of the M1729 family are unconditionally stable. 



It is of interest to note that spreads of the order of ±20 to ±25 per 

 cent are of the same magnitude as those dispersions now existing amongst 

 the characteristics of presently available well-controlled electron tubes. 

 These kinds of data on reproducibility of the linear equivalent circuit 

 element values hold for practically all classes of point-contact devices 



Fig. 14 — Stability contour and ranges of a and rt . 



now under development for cw transmission service. While it is too 

 early to prove that such a situation pertains as well to junction tran- 

 sistors, there is every reason to expect similar results after a suitable 

 development period. 



Reproducibility of Large-Signal Characteristics for Pulse Application 



When electron devices are employed for large-signal applications, 

 particularly those of switching and computing, it is well known that the 

 characteristics must be controlled over a very broad range of variables 

 from cutoff to saturation. In September, 1949, very little attempt was 

 made to control such pulse use characteristics. In the intervening time, 

 transistor circuit studies have proceeded to the point where it is possible 

 to define certain necessary large scale transistor characteristics which, 

 if met, permit such transistors to be used interchangeably and repro- 

 ducibly in a variety of pulse circuit functions such as binary counters, 



