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.
