Transistor Biasing In the Active Region

• Biasing is the process of applying external voltages to the     transistor.The two junctions in a BJT must be biased properly in   order to operate it as an amplifier. A transistor cannot work unless   external DC power supply are connected to it.
• A BJT is capable of operating in  four different region,depending    on the way in which it is biased.
  The region of operation are:
 1. Cuttoff region (transistor is OFF)
 2. Saturation region (transistor is Fully ON)
 3. Forward active region (in between saturation and cutoff).
 4. Inverse active mode
Forward active region these four region of operation are :

Table : Biasing Condition for different region of operation.

• The biasing of transistor for active region as shown in the table transistor should be biased in the forward active region so as to operate it as an amplifier.

•The above table also indicates the conventional directions of the currents IC, IB & IE plus the polarities of voltages VBE and VCE 

Fig.Transistor biasing for active region

•In order to use the transistor as an amplifier, it must be operated in its active region. The biasing of P-N-P and N-P-N transistors for their active region operation and the directions of the currents as shown in the fig. bellow.

Fig.Transistor biasing in the active region.