434 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



Power Requirements 



The transistor, of course, has the inherent advantage of requiring no 

 heater power; moreover, significant advances have been made in the past 

 two years in reducing the collector voltage and power required for prac- 

 tical operation. Consider the minimiun collector voltage for which the 

 small-signal Class A gain is still within 3 to 6 db of its full value. In 

 September, 1949, the type A transistor could give useful gains at col- 

 lector voltages as low as 30 volts. Today, several point-contact devices 

 (M1768 and M1734) perform well with collector voltages as low as 2 to 

 6 volts even for relatively high-freciuenc}^ operation. One junction tran- 

 sistor, the j\I1752, can deliver useful gains at collector voltages as low 

 as 0.2 to 1.0 volt. Under these same conditions, the minimum collector 

 power for useful gains may be as low as 2-10 mw for point-contact 

 devices and as low as 10 to 100 /xw in the case of the junction transistors.* 

 Class A efficiencies have been raised for the point -contact devices to as 

 high as 30-35 per cent and for junction transistors this may be as high 

 as 49 per cent out of a maximum possible 50 per cent. Class B and C 

 efficiencies are correspondingly close to their theoretical limiting values. 



PERFORMANCE STATUS 



Exact electrical performance specifications for the transistor depend, 

 of course, upon the intended applications and the type of transistor 

 being developed for such an application. These types are beginning to 

 be specified; and in fact, they are already so numerous that mention of 

 only a few salient features of some of them will be attempted. Bear in 

 mind, as was pointed out before, that no one transistor combines all 

 the \drtues any more than does any one tube type. Fig. 26 attempts to 

 compare the progress made in se^'eral important performance merit 

 figures by development of several point-contact and junction types 

 during the last two years. Again the reference performance is that of 

 the type A as of September, 1949. 



Some switching and transmission applications need transistors having 

 high current gain. By gouig to a point-junction structure, useful values 

 of alpha as high as 50 are now possible with laboratory models. 



For straight transmission applications, the single stage gain of point- 

 contact types (Ml 768, M1729) has been increased to 20-24 db, whereas 

 for the M1752 junction type the single stage gain may be as high as 

 45-50 db. 



* In some special cases, depending upon the application, practical operation 

 may be obtained for as little as 0.1 to 1.0 microwatt. 



