Reading from Chapter 4

Bipolar Junction Transistor

• An npn BJT has two layers of n-type material, known as the collector and emitter, and in between a layer of p-type material, known as the base.
• In order for a BJT to have a good performance, the base current needs to be small compared to the collector current.

$\beta =i_{C}/i_{D}$

• Operation in the active region:

*The base-emitter junction is forward biased.
*The base-collector junction is reverse biased.

• As amplifiers, BJTs operate in the active region.
• As switches, BJTs operate in saturation and cutoff.