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The forward biased
base/emitter junction
causes electrons to be
attracted from the
emitter area towards the
base.
Arriving in the base
area, most of the
negative electrons come
under the influence of
the more positive
collector and are
attracted by it.
This is shown in the
left hand drawing, where
the base current plus
collector current equals
the emitter current.
Alpha gain is collector
current divided by
emitter current, and is
always less than 1.
Beta gain is collector
current divided by base
current and can be a
fairly high number.
Therefore, causing a
small base current to
flow makes a much larger
collector current flow.
A small base current
controls a large
collector current.
There is 0.6 volts
across the base/emitter
junction, when it is
forward biased. (0.3
volts for germanium).
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