836 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



In an n-p-n transistor the collector and emitter terminals are the posi- 

 tive electrodes of the rectifiers, see Fig. 7(a), and in a p-n-p transistor 

 the collector and emitter terminals are the negative electrodes of the 

 rectifiers, see Fig. 7(b). The base terminal is the common point of the two 

 rectifiers. In a given transistor each rectifier has a satin'ation voltage, 

 usually stated in the characteristics, which must not be exceeded in 

 normal operation. Thus, the saturation voltage of the collector rectifier 

 determines the maximum instantaneous collector potential. The emitter 

 rectifier also has a saturation voltage which determines the maximum 

 potential which can be applied between the base and the emitter. The 

 saturation voltage of the collector rectifier usually differs from the 

 saturation voltage of the emitter rectifier. 



2.32. Transistor Action 



If a source of potential, Ece in Figs. 7(a) and 7(b) is connected between 

 the collector and emitter terminals, the resulting current will flow in 

 series through the collector rectifier in its reverse direction and through 

 the emitter rectifier in its forward direction. This is the direction of 

 current flow for transistor action to take place. In Fig. 7 the reverse 

 resistances of the collector rectifiers are sho^vn and the forward resist- 

 ances of the emitter rectifiers are also shown. 



Ece -^- 



COLLECTOR 

 TERMINAL 



EMITTER 

 TERMINAL 



COLLECTOR 

 RECTIFIER 



EMITTER 

 RECTIFIER 



FORWARD 

 RESISTANCE . 

 OF EMITTER. 



REVERSE 



RESISTANCE 



OF COLLECTOR 



BASE 

 TERMINAL 



AAA ? 



FORWARD 

 RESISTANCE , 

 OF EMITTER, 



H 



EMITTER 

 RECTIFIER -' 



RESISTANCE 

 OF BASE 



EMITTER 

 TERMINAL 



COLLECTOR 

 RECTIFIER 



''1 



REVERSE 



RESISTANCE 



OF COLLECTOR 



COLLECTOR 

 TERMINAL 



(a) n-p-n transistor (b) p-n-p transistor 



Fig. 7 — Junction transistor analogj'. 



1 



