Due to forward biasing of emitter-base
junction, majority carriers (Electrons) flow towards base. A big amount of
electrons cross the junction and enter the base. As the base is lightly doped,
so a small amount (2 to 5 percent) of electrons recombine with holes in the base
and almost more than 95 percent electrons come under the effect of positively
charged collector and enter the collector. This is possible due to attraction
of collector voltage.
As collector-base junction is reverse
biased, so electrons cannot flow from collector to base due to high resistance,
infect, electrons always flow from base to collector.
Thus
due to diffusion and collection of electrons (provided by emitter) in the
collector-base junction, the flow of electronic current starts. The direction shown
in figure shows the flow of conventional current.
This should be kept in mind that the
transistor will not conduct unless its emitter-base junction is forward biased.
Figures,
 |
| Biasing of NPN Transistor |
 |
| Biasing of NPN Transistor (Symbol, Circuit Diagram) |
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