DIFFUSED EMITTER AND BASE SILICON TRANSISTORS 



9 



0.98 



0.94 



0.90 



0.86 



a 



0.82 



0.78 



0.74 



0.70 



0.1 0.2 0.4 0.6 1 2 4 6 8 10 20 



CURRENT, Ig, IN MILLIAMPERES 



Fig. 7 — Alpha as a function of emitter current and temperature for a double 

 diffused silicon n-p-n transistor. 



under this condition does not truly saturate but collector junction re- 

 sistance is very high. Collector junction resistances of 50 megohms at 

 reverse biases of 50 volts are common. 



The continuous power dissipation permissible with these units is also 

 shown in Fig. 6. The figure shows dissipation of 200 milliwatts and the 

 units have been operated at 400 milliwatts without damage. As illus- 

 trated in Fig. 3 no special provision has been made for power dissipation 

 and it would appear from the performance obtained to date that powers 

 of a few watts could be handled by these iniits with relatively minor 

 provisions for heat dissipation. However, it can also be seen from Fig. 6 

 that at low collector voltages alpha decreases rapidly as the emitter 

 current is increased. The transistor is, therefore, non-linear in this 

 range of emitter currents and collector voltages. In many applications, 

 this non-linearity may limit the operating range of the device to values 

 below those which would be permissible from the point of view of con- 

 tinuous power dissipation. 



Fig. 7 gives the magnitude of alpha as a function of emitter current 

 for a fixed collector voltage of 10 volts and a number of ambient tem- 

 peratures. These curves are presented to illustrate the stability of the 

 parameters of the double diffused silicon transistor at increased ambient 

 temperatures. Over the range from 1 to 15 milliamperes emitter current 

 and 25°C to 150°C ambient temperature, alpha is seen to change only 



