Transistor Resistance

Thread Starter

SamR

Joined Mar 19, 2019
5,078
@Danko Yes that clearly shows something happens @ ~320Ω. I'm tempted to go back and reproduce my circuit and take smaller incremental measurements from 200-400Ω and around 600Ω but your simulation graph also clearly shows it around 320Ω. What happened? The other aberration @ ~600Ω in my experimental data is also curious. I have not studied the Eber-Molls or other such models. Do they come into play here?
 

Danko

Joined Nov 22, 2017
1,855
Yes that clearly shows something happens @ ~320Ω. I'm tempted to go back and reproduce my circuit and take smaller incremental measurements from 200-400Ω and around 600Ω but your simulation graph also clearly shows it around 320Ω. What happened?
@ 320Ω transistor becomes fully ON (saturated, shorted) and works as piece of wire.
After 320Ω overall resistance is almost equal to resistance of R1, because resistance of C - E is close to zero.
The other aberration @ ~600Ω in my experimental data is also curious.
Something wrong with measurements... I think your next measurements will much more accurate.
Simple simultaneously measure voltage C - E and current of R1, as shown in post #18.
I have not studied the Eber-Molls or other such models. Do they come into play here?
Circuit simulated in LTspice, about used models you can read here: http://ltwiki.org/index.php?title=Q_Bipolar_transistor
 
Last edited:

Thread Starter

SamR

Joined Mar 19, 2019
5,078
@ 320Ω transistor becomes fully ON (saturated, shorted) and works as piece of wire.
Aha! Got it, thanks Danko. Still a very minor resistance in addition to Rc but nearly zero. Yes, I was a bit suspicious of the higher reading and if it had been the only one would have assumed it was just a "flyer" and ignored it. Thanks again!
Sam
 
Top