[sdiy] Transistor help

[René Schmitz]

Hi Ian and all,

Sure you can relate base current to base voltage by the diode equation. 
Essentially Vbe ~ c * log(Ib). And if your hFE meter does measure the 
base current for a constant collector current, asumed c is the same for 
two transistors, it will be correlated. Only the resolution is a 
problem, because you don't measure on a linear scale.

I'd rather trust a diode tester, and measure Vf for the base emitter 
diode. (I.e. measure at Ic = 0).


Cheers,
  René

Ian Fritz wrote:
> At 11:16 AM 4/26/05, René Schmitz wrote:
> 
>> hFE is not the right way to select matched pairs.
> 
> 
> Did you ever try it? :-)
> 
> I have found a strong correlation between hFE and Vbe at constant 
> current.  I say it works OK!  And much easier than building a special 
> circuit.  Remember, an hFE function on meters was not common 25 years ago.
> 
>   Ian
> 
> 
> 
> 

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159