Why is it universally stated in so many places that the Base Current Ib controls the collector current Ic in a Bipolar Junction Transistor when I guess it is pretty obvious that its the Emitter Base forward bias voltage that will be responsible for the change in the base current.. Making the Vbe controlling factor of Ic.. It is all very confusing
Voltage does not cause current, current does not cause voltage, at least for any meaningful understanding of the word 'cause'. They both co-exist.
When the base-emitter junction of a transistor is biassed, an Ib flows into the base, while a VBE exists across it.
If we now measure the collector-emitter current, we find the ratio to the base current is more or less constant over a very wide range, many orders of magnitude. This is sufficiently useful that engineers call this ratio beta.
The ratio of collector current to VBE varies with the base current. The ratio of them is still useful, engineers call it the transconductance or gm of the transistor, but it's valid at only one base current setting. So while the BJT is also voltage controlled, as the relationship is non-linear, it's not useful for doing calculations for the initial biassing of the transistor, which usually involves comparing currents over a wide range.
This means that when biasing up a transistor, the beta×Ib expression is most useful for collector current. When using a biased transistor as an amplifier, the gm×VBE expression is frequently used.
Nullbyte, I agree with you, the situation seems to be confusing because some books/articles state that the BJT would be current-controlled and some other say voltage-controlled. This is a very unsatisfying situation - I really cannot understand, why some (many) people still think (no - they only believe) that the BJT would be current-controlled. There is not a single proof for this claim. Can you imagine how two additional charged carriers in the base region should be able to release 1000 additional carriers from the emitter (assuming B=500)?
In contrary - there are many explanations and effects which clearly show that the collector current Ic of a BJT is - of course - controlled by the base-emitter voltage Vbe.
It is really a phenomenon - all designers of classical BJT-based gain stages assume voltage control (low-resistive base voltage divider, voltage-feedback of the emitter resistor Re), but some of them - without realizing what they were doing - still believe in current-control. Don`t ask me why - I cannot answer.
One explanation may be the fact that for CALCULATION PURPOSES it sems to be simple and convenient to ASSUME current control - and, inded, it works! However, we should not mix physical principles with design-oriented methods.
As a background, I like to give you a similar example:
We say that in a simple resistive voltage divider the current would produce a voltage across each of the two resistors in proportion to the resistor values (given in Ohms) - right?
No - physically wrong. A current cannot produce this voltage. It is always the voltage that allows/drives a certain current. And the voltages are a only measure of the electric fields within the two resistors. Hower, for calculation purposes, we are allowed to say: The total current produces a voltage V=IxR. But physically, in the cause-and-effect sense this is wrong.
And the same applies to the base current Ib=Ic/B ...it is a by-product that cannot be avoided. And for calculation/design purposes we may use this equation in the form Ic=Ib*B. But this does not mean that Ic would be controlled by Ib.
It's because current is a defining factor in the relationship between the base-emitter junction and collector current and it makes the most sense to use current here. It's effectively a diode and adding a voltage supply greater than it's saturation voltage without a resistor between them is like shorting it. Sure you could use the diode equation to relate voltage and current here but that only makes it more confusing.
Contrast this to a MOSFET where the gate is an insulator and doesn't allow current through it (ignoring capacitance and leakage current, which aren't relevant to the concept). The MOSFET is literally a voltage controlled device, the voltage is the defining factor in the drain current.