Question

With circuit diagram, explain working of CB amplifier?

Answer 1

The voltage divider biasing is used biasing CB amplifier. Emitter base junction is forward biased by voltage across R, and the collector base junction is reverse biased by the voltage across R_r Coupling capacitors block DC and allow AC to pass through. By pass capacitor C_B by passes AC.

During positive half cycle of input signal, forward bias on the base emitter junction decreases as it is reverse biased,Hence I_c and I_CR_C is decreased.The output voltage V_CB is increased because V_CB = V_cc – I_CR_C. Thus positive half cycle is obtained at the output.

During negative half cycle of the input signal, forward bias on base emitter junction is increased. Hence I_E, and I_c increase and I_C,R_C also increases. As V_CB = V_cc – I_cR_r, V_CB decreases as LR_r increases. Thus negative half cycle of output is obtained. The input and output signals are in phase.