PRESENT STATUS OF TRANSISTOR DEVELOPMENT 



ir 



family whicli gixcs tlic (l('{)(MhkMicc of collector volta|i;(' upon oollector 

 cuncMit with emitter eiirreiit ms parameter. These characteristics may 

 he thought of as the dual to the phitc family of a triocle.'- The slope 

 of these curves is very nearly the small-signal ac (u)llcctor impedance of 

 the transistor.* For a fixed collector N'oltage of —20 volts, when the 

 emitter current is changed from zero to one milliampere, note that the 

 collector current correspondingly changes slightly more than two 

 niilliampcrcs, indicating a current gain, alpha, of slightly more than 

 t wo. 



Xewest memhei' of the transistor family ret^entl}' d(>scril)ed by Shock- 

 ley, Sparks, Teal, Wallace and Pietenpol is the n-p-n junction tran- 

 sistor. ' Fig. 5 is a schematic diagram of such a structure. In the center 

 of a bar of single crystal n-type germanium there is formed a thin layer 



SINGLE-CRYSTAL 

 /-"'GERMANIUM BAR 



COLLECTOR 



T 



p-TYPE 



Fig. 5 — The n-p-n junction transistor 



PRIMARY EMITTER CONTROLLED 

 ELECTRON CURRENT 



COLLECTOR 

 JUNCTION 



B! 



SMALL RESIDUAL 



COLLECTOR 



REVERSE CURRENT 



'not CONTROLLED BY 



emitter) 



Fig. 6 — Schematic diagram of a junction transistor. 



* As shown by Rj-der and Kircher,' the ac collector impedance, Tc = R22 — R12, 

 where R-v. is the open-circuited output imj)edance and Rij is the open-circuit feed- 

 hack impedance. Usually, R22 3> R12. 



