You are really missing something. I cannot figure out how turning the potentiometer can affect the base current.View attachment 169155
All those PWM suggestions are good, but this seems to really simple, perhaps I am missing something.
But for DC bias and large signal/switching design it works better to consider the BJT as a black-box current-controlled current-source with a low input-impedance (as a forward biased diode), using the current-gain (Beta or hFE) for the calculations.
Of course then we have to deal with beta dependence on T which gives us grief. DrivingHi,
I agree that a BJT is voltage driven.
But if you drive it with a constant voltage you get thermal drift problems.
Since V_BE drifts with about -2mV/K you need to modify the drive voltage with the same -2mV/K.
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If one "wrongly ?" treats the BJT as current driven ... one reduces/avoids this problem.
*****
It´s good to know the details, the benefits and drawbacks, so one can use the one or the other method.
Klaus
If you look at the device, the current carriers injected at the base is the single most important controlling factor of the collector current.*****
If one "wrongly ?" treats the BJT as current driven ... one reduces/avoids this problem.
*****
It´s good to know the details, the benefits and drawbacks, so one can use the one or the other method.
Klaus
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