A HIGH-FREQUENCY DIFFUSED BASE GERMANIUM TRANSISTOR 27 



40 



30 



10 



_l 



LU 



5 20 

 o 



LJJ 



Q 



10 



-10 



0.1 0.2 0.4 0.6 1 2 4 6 e 10 20 40 60 100 200 400 1000 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 2 — The grounded emitter and grounded base response versus frequency 

 for an exceptionally good unit. 



to 20 ohms and a junction transition capacity of 1 fx^xid were measured. 

 The displacement current which flows through this transition capacity 

 reduces the emitter efficiency and must be kept small relative to the 

 injected hole current. With 1 milliampere of ciu"rent flowing through the 

 emitter junction, and conseciuently an emitter resistance of 26 ohms, 

 I the emitter cutoff for this transistor was above 6,000 mc/sec. One can 

 now see that the emitter area must be small and the current density 

 high to attain a high emitter cutoff freciuency. The fact that a low base 

 resistance requires a high level of doping in the base region, and thus a 

 high emitter transition capacity, restricts one to small areas and high 

 current densities. 



In the collector circuit capacities of 0.5 to 0.8 ^l^xid at a collector volt- 

 age of — 10 volts were measured. There was a spreading resistance in the 

 collector body of about 100 ohms which was the result of the small 

 emitter area. The base resistance was approximately 100 ohms. If the 

 phase shift and attenuation due to the transport of minority carriers 

 through the base region w^ere small at the collector cutoff frequency, the 

 (effective base resistance would be decreased by the factor (1 —a). The 

 collector cutoff frequency is then given by 





where Cc = collector transition capacity 



and Re = collector body spreading resistance. 



