explain DC Biasing - BJT, Transistor Bias Stabilization, Transistor biasing

Biasing - shifting the mean operating point. To avoid operation in
 Non-linear region
Saturation region
 Cut-off region
Max. power consumption


Linear region operation
Base-emitter forward bias
Base-collector reverse bias
Cutoff region
Base-emitter reverse bias
Saturation region
Base-emitter forward bias
Base-collector forward bias

Used to compensate for temperature effects which affects semiconductor operation.  As temperature increases, free electrons gain energy and leave their lattice structures which causes current to increase.

Requirements upon biasing circuit :
The operating point of a device, also known as bias point or quiescent point (or simply Q-point), is the DC voltage and/or current which, when applied to a device, causes it to operate in a certain desired fashion.

For analog circuit operation, the Q-point is placed so the transistor stays in active mode (does not shift to operation in the saturation region or cut-off region) when input is applied. For digital operation, the Q-point is placed so the transistor does the contrary - switches from "on" to "off" state. Often, Q-point is established near the center of active region of transistor characteristic to allow similar signal swings in positive and negative directions.

Q-point should be stable. In particular, it should be insensitive to variations in transistor parameters (for example, should not shift if transistor is replaced by another of the same type), variations in temperature, variations in power supply voltage and so forth.
The circuit must be practical: easily implemented and cost-effective.