If a positive voltage (>0.6V) is
applied to the base of an npn
transistor, the pn junction between
the base and emitter becomes
forward-biased. During forward
bias, escaping electrons are drawn
to the positive base.
• Some electrons exit through the
base, but because the p-type base
is so thin, the onslaught of
electrons that leave the emitter get
close enough to the collector side
that they begin jumping into the
collector. Increasing the base
voltage increases the emitter-tocollector
electron flow.
• Recall, positive current flow is in
the direction opposite to the
electron flow current flows from
collector to emitter.