[sdiy] Measuring Rbe

sdiy sdiy at haraldswerk.de
Wed Jun 8 18:14:32 CEST 2011


I tried to measure Rbe on some transistors using the method of Rene Schmitz 
described on his website http://www.uni-bonn.de/~uzs159/

"The procedure is to measure Vce (collector is open) while variing the base 
current from a few hundered micro amps to about 5 miliamps. I used a set of a 
few fixed resistors in the range from 1k to 15k for the base current. The Rbe 
is the high current slope of the Vce vs Ib graph."
end quote

I followed the description above. Emitter on ground. Basis at +10V with 
varying the R in one k steps from 1k to 30k. Collector open. Then calculating 
deltaVce / deltaIb to become Rbe
Measuring an CA3046 at 26degCelsius I calculated Rbe at about 7Ohm. That is 
near what Rene measured.
I will give the other figures i did when the method is confirmed.

But i am not sure if i understand it right. I am wondering why i can measure  
Vce when the collctor is open? Can anyone shet some light on this?


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