GATE 2014 EC (EC2) – Question 23
Two cascaded voltage amplifiers are shown. A1 has open-loop voltage gain 10, input resistance 10 kΩ, output resistance 1 kΩ. A2 has corresponding values 5,5 kΩ,200 Ω. Find approximate overall gain vout/vin.
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Correct answer: 34.0 to 35.3
Explanation
The first stage’s unloaded gain10is reduced by the divider Rin2/(Ro1+Rin2)=5k/6k. The second gain5is reduced by RL/(Ro2+RL)=1k/1.2k. With the ideal input-voltage source shown, total gain=10×(5/6)×5×(5/6)=**34.7222**. Multiplying unloaded gains alone would give50.