question_answer

By increasing the load resistance, can we increase the voltage gain \[({{A}_{V}}=-{{g}_{m}}{{R}_{L}})\] of an amplifier indefinitely? Or Explain the effect of increasing load resistance R, on the voltage gain of a transistor amplifier.

Answer:

                    Initially, the voltage gain\[({{A}_{V}}=-{{g}_{m}}{{R}_{L}})\] increases with the increase in load resistance \[{{R}_{L}}\]. But the gain of an amplifier cannot be increased indefinitely by increasing \[{{R}_{L}}\]. We know that \[{{V}_{CE}}={{V}_{CC}}-{{I}_{C}}{{R}_{L}}\] If we increase \[{{R}_{L}},{{V}_{CE}}\]decreases and if \[{{V}_{CE}}\] becomes less than \[{{V}_{BE}},\]  both the junctions get forward biased and saturation starts.