Is it possible for the base current to exceed the collector current for a BJT in saturation mode? (If the base current was increased without the collector current increasing at all)
Electronic – BJT in Saturation
bjtsaturationtransistors
Related Solutions
Remember the V(CE) vs I(C) curve and consider an NPN transistor. Thus forward biasing simply means there is positive voltage on the p-type junction relative to an n-type junction.
Thus, in our case forward biasing the BC junction means having a voltage V(BC) > 0.
Now, when collector voltage V(C) drops below the base voltage V(B) and forward biases the collector‐base junction (when V(BC) > 0):
The strong electric field which opposes the movement of the charged particles into the collector is now weakened.
There is now a numerous charged particles into the collector, hence current increases and the current gain factor, β, decreases.
This corresponds to a logical more of "0" where the transistor acts as a switch, showing a low resistance path for current conduction.
You have understood this correctly and it appears the author of the document you linked is wrong - for a MOSFET they have perfectly described the saturation region but, this is a BJT circuit and the saturation region is the left hand side. Here's the drawing they talk about: -
Saturation is when the current and voltage rise almost linearly together for a fixed base current.
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Best Answer
It is possible. Consider the figure below.
The collector current at saturation will be $$I_{Csat} = \frac{V_{CC}-V_{CEsat}}{R_C} \approx \frac{V_{CC}}{R_C}$$
The base current is given by, $$I_B = \frac{V_{CC} - V_{BE}}{R_B} \approx \frac{V_{CC}}{R_B}$$
So it is clear that the currents at saturation are entirely decided by the resistors and hence base current can be greater than the collector current at saturation.