PRESENT STATUS OF TRANSISTOR DEVELOPMENT 



425 



hit registers, regenerative pulse amplifiers, pulse delay amplifiers, gated 

 amplifiers and pulse generators. Moreover, it has been possible to meet 

 these requirements on a developmental \v\v\ with good yields in at 

 least three types of point-contact switching transistors. The scope of 

 this paper will not permit a detailed accounting of the technical features 

 of this situation and such an account will be forthcoming in future papers 

 on these particular studies. However, a brief description of some of the 

 more important i)ulse characteristics and their tolerances is certainly 

 l)ertinent. 



In practically all of the transistor pulse handling circuits examined to 

 date, one characteristic common to all is the ability of the transistor, by 

 N'irtue of its current gain, to present various types of two-state negative 

 resistance characteristics at any one or all of its pairs of terminals. A 

 typical simple circuit and corresponding characteristic is shown in Fig. 

 15 for the emitter-ground terminals when a sufficiently large value of 

 resistance is inserted in the base to make the circuit unstable. In region 

 I where the emitter is negative, the input resistance is essentially the 

 reverse characteristic of the emitter as a simple diode. In region II as 

 the emitter goes positive, alpha, the current gain rises rapidly above 

 luiity. If Rb is sufficiently large and alpha, the current gain, is greater 



REGION I 

 (CUT-OFF) 



REGION HI 

 (SATURATION) 



Fig. 15 — Emitter-ground negative resistance rircuit and characteristic. 



