• Why is emitter bias more stable than base bias?

Emitter bias is more stable than base bias because it involves  biasing the emitter terminal of the transistor to a fixed voltage, while  the base-to-emitter voltage is varied. This method provides negative  feedback that stabilizes the operating point of the transistor, making  it less sensitive to variations in temperature and other parameters.

• Explain why the base bias Q-point changes with temperature.

One factor is the change in the base-to-emitter junction voltage  (Vbe) with temperature. Vbe is a temperature-sensitive parameter that  changes with temperature and is proportional to the bandgap voltage of  the semiconductor material used to make the BJT. As temperature  increases, Vbe decreases, which results in a change in the DC operating  point (Q-point) of the transistor. Another factor is the change in the  forward beta (β) of the transistor with temperature. β is the current  gain of the transistor, which decreases with temperature due to a  reduction in the doping level in the base region of the transistor. This  reduction in β leads to a change in the current gain of the transistor  and, as a result, changes the Q-point.

• How does emitter-feedback bias improve on base bias?

Emitter-feedback bias improves upon base bias by providing more  stability to the operating point of a bipolar junction transistor. The  emitter-feedback bias configuration involves connecting a resistor  between the emitter and the base of the transistor.