Neet Solved Paper 2013 Question 44
Question: In a common emitter (CE) amplifier having a voltage gain G, the transistor used has trans conductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with trans conductance 0.02 mho and current gain 20, the voltage gain will
Options:
A) $ \frac{2}{3}G $
B) $ 1.5G $
C) $ \frac{1}{3}G $
D) $ \frac{5}{4}G $
Show Answer
Answer:
Correct Answer: A
Solution:
- As $ A _{v}=\beta \frac{R _{L}}{R _{i}} $ $ [ \because g _{m}=\frac{\Delta l _{c}}{\Delta V _{B}}=\frac{\Delta l _{c}}{\Delta l _{B}R _{i}} ] $ or $ G=( \frac{\beta }{R _{i}} )R _{L} $ $ [ \because g _{m}=\frac{\beta }{R _{i}} ] $
$ \Rightarrow $ $ G=g _{m}R _{L} $
$ \Rightarrow $ $ G\propto g _{m} $
$ \therefore $ $ \frac{G _2}{G _1}=\frac{{g _{m _1}}}{{g _{m _2}}} $
$ \Rightarrow $ $ G _2=\frac{0.02}{0.03}\times G $
$ \therefore $ Voltage gain $ G _2=\frac{2}{3}G $
BETA
