Hope it makes sense to you?
Adam
Hi Adam - for my opinion you didn´t really met "my point". Let me explain:
As the result of your contribution we have two formulas which - for my opinion - cannot be compared to each other.
That means: They cannot reveal any differences between both approaches.
The
first equation describes the physical behaviour of the pn junction, that means: How the collector current depends on the applied base-emitter voltage.
Nobody would use this equation for designing an amplifier stage. Nevertheless - it reflects the physical truth.
The
second equation shows how in practice the current limiting resistor RB is calculated. In words: The formula shows how a base-emitter voltage of VBE=0.6 V can be created if a DC source of 5V is available. For this purpose, we are using a resistor RB in series with the B-E path. The value for RB is calculated using the current through it (IB). You will notice that in my last contribution I have mentioned exactly the same formula.
Question: Is this method to produve VBE=0.6 V something that can be called "current- control?".
That is my main point: Everybody is using the same set of formulas - however, some people think that they exploit a current-control feature of the BJT. But this is not true!
Even the last example presented by you is based on the requirement to create the necessary voltage VBE.
Last comment: Of course, you can argue that - if we all use the same formulas - it does not matter if we call this procedure "current" or "voltage" control.
Let me explain why I think it is important to use the correct description and the correct wording:
Up to now I have seen no physical explantion WHY the base current IB should be able to control IC. This is no surprise because it cannot be justified.
More than that, also from the energy point of view it is impossible that a certain quantity (in our case IB) can directly control a larger quantity of the same kind (in our case: IC).
The only relation we have is IB=IC/B - however, this simple relation does only state that IB is a fraction of IC and does not tell us anything about Ic control.
In general, it is my opinion that students should start learning to be critical against simple equations and simple explanations.
I think, they shouldn´t simply believe something and - as often as possible - they should ask „why?“. This is the first step to really
understand how an electronic circuit works.
Therefore, I think it is important to realize the physical truth behind the formulas we are using.