1002 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1957 



consider the spread of breakdown voltage, the data was normalized to 

 the instantaneous power required to turn on a negative resistance. This 

 turn-on power was the turn-on power multiplied by the voltage. 



Fig. 17 is a plot of the distributions of turn-on power for the rectifiers 

 which had a negative resistance plotted as a log normal distribution on 

 probability paper. The median value for the turn-on power is 1.2 watts. 

 Eighty per cent of these diodes went into a negative resistance condition 

 at powers between 0.1 and 10 watts. Many diodes could dissipate several 

 kilowatts with no negative resistance. These were not included. 



Experiments show that devices which show surface breakdown will 

 collapse at power levels which are orders of magnitude below that ob- 

 served for devices in which body breakdo^Mi is observed. 



The picture is more cloudy with smaller area rectifiers (area •^ 10"^ 

 cm"). In these devices it was not possible to predict the pulse properties 



< 



OI 



5 



o 



a 



40 



20 



0.2 



0.1 

 0.08 

 0.06 



10 20 30 50 70 80 90 95 99 



DISTRIBUTION 



Fig. 17 — The distribution of turn-on power for rectifiers {A ^^ 10~^ cm^) in 

 which a negative resistance is observed plotted a.s a log normal distribution on 

 probability paper. 



