Electronics - Bipolar Junction Transistors (BJT) - Discussion

The voltage divider is formed using external resistors R1 and R2. The voltage across R2 forward biases the emitter junction. By proper selection of resistors R1 and R2, the operating point of the transistor can be made independent of β. In this circuit, the voltage divider holds the base voltage fixed independent of base current provided the divider current is large compared to the base current. However, even with a fixed base voltage, collector current varies with temperature (for example) so an emitter resistor is added to stabilize the Q-point, similar to the above circuits with emitter resistor.

For an transistor input has voltage across R2 so operating point does not depend on beta. And has stable always.

See we want stable Q point always. And for that only we use voltage divider biasing technique.

But what is the mean of Q point and voltage divider bias? Please explain.

Q point depends on collect-emitter voltage(x axis) and collector current (y axis)--as the fixed biased base is a part of voltage divider the base current remain constant due to which In and vbe remain constant.