• Print
• Login

Current Flow Model

<^< Transistor Operation | Course Index | Examples: Current Flow Model >^>

Mobile electrons in the emitter region are attracted to the more positive potential present at the base. When these electrons enter the base region most are swept across into the collector region that has a higher positive potential than the base (remember that the base region is made very narrow). A few electrons recombine with vacant holes in the base. This results in a small current flow in the base. A much larger current flow appears in the emitter and collector.

The typical currents in the diagram show that:

• Collector current = 1.9 mA
• Base current = 0.1 mA
• Emitter current = 2.0 mA

Note that electron flow and conventional current flow are in opposite directions. Hence, electron flow out of the collector is equivalent to current flow into the collector. We have shown the direction of current flow using arrows.

By applying Kirchhoff's Current Law we can conclude that:

Emitter current = Base current + Collector current

<^< Transistor Operation | Course index | Examples: Current Flow Model >^>