DIFFUSED EMITTER AND BASE SILICON TRANSISTORS 



z 

 < 



o 



I- 



z 



LJ 



a. 

 cr 



D 

 O 



40 



30 



20 



(0 



-\0 



-20 



-30 



0.1 0.2 0.5 1.0 2 6 10 20 50 100 200 



FREQUENCY IN MEGACYCLES PER SECOND 



500 1000 



Fig. 4 — ■ Short-circuit current gain of a double diffused silicon n-p-n transistor 

 as a function of frequency in the common emitter and common base connections. 



Fig. 5 shows a high-freciueiicy lumped constant equivalent circuit 

 for the double diffused silicon transistor whose current gain cutoff char- 

 acteristic is shown in Fig. 4. External parasitic capacitances have been 

 omitted from the circuit. The configuration is the conventional one for 

 junction transistors with two exceptions. A series resistance rj has been 

 added in the emitter circuit to account for contact resistance resulting 

 from the fact that the present emitter point contacts are not perfectly 

 ohmic. A second resistance r/ has been added in the collector circuit to 

 account for the ohmic resistance of the n-type silicon between the col- 

 lector terminal and the effective collector junction. This resistance exists 

 in all junction transistors but in larger area low frequency junction 

 transistors its effect on alpha-cutoff is sufficiently small so that it has 

 been ignored in equivalent circuits of these devices. The collector RC 



Ce = TmmF 



Pq -]AU) 



Cc = 0.52//^F r ' _ ,50 co 



Tg = 150; 



a 



J^C( 



•Le 



'%=QOCO 



COMMON BASE CURRENT 

 GAIN CUT-OFF FREQUENCY 



■ 120 MC 



Ic = 3 MA 

 Vc = 10 VOLTS 



Fig. 5 ~ High-frequency lumped constant equivalent circuit for a double 

 diffused silicon n-p-n transistor. 



