JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELECTRONIC CIRCUITS Previous Question Paper (March - 2022 - R15)
Answer any five questions. All Questions Carry Equal Marks.
Main
Mention the significance of Gain-Bandwidth product of amplifiers.
Answer
The Gain-Bandwidth Product (GBW) is a fundamental figure of merit for an amplifier, representing the product of the open-loop gain and the bandwidth at which that gain is measured. Its significance lies in the trade-off between gain and frequency response: for a given amplifier design, the product remains constant, meaning any increase in gain results in a proportional decrease in bandwidth. It allows engineers to determine the maximum frequency at which an amplifier can provide a useful gain and serves as a primary specification for selecting operational amplifiers for high-frequency or wideband applications.
An amplifier consists of 3 identical stages in cascade. The bandwidth of overall amplifier extends from 20 Hz to 20 kHz. Calculate the bandwidth of individual stage.
Answer
For an amplifier consisting of n identical stages, the overall bandwidth
- Calculate the bandwidth reduction factor: √(21/3 - 1) ≈ √(1.2599 - 1) ≈ √0.2599 ≈ 0.51
- Determine individual stage bandwidth: f2(stage) = 20 kHz / 0.51 ≈ 39.22 kHz
Thus, the bandwidth of each individual stage is approximately 39.22 kHz.
Differentiate CC, CB, CE amplifiers.
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Prove that the mid band gain of an emitter follower circuit is approximately equal to unity.
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For a single stage CE amplifier with RS = 1K, R1 = 50 K, R2 = 2 K, RC = 1K, RL = 1.2K, hfe = 50, hie = 1.1K, hie = hoe = 0; find AI, Ri, Ro, AV and power gain.
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Discuss the classification of amplifiers based on feedback and write the Effect of feedback on Amplifier characteristics.
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An amplifier without feedback has a voltage gain of 50, input impedance 1kΩ and output impedance 2.5kΩ. Obtain the input and output impedances of current-shunt negative feedback amplifier using the above amplifier with a feedback factor of 0.2.
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Draw the circuit diagram of a Wein bridge oscillator. Explain how Barkhausen criterion for oscillation is satisfied by the circuit and derive an expression for the frequency of oscillation.
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Draw the circuit diagram of a Colpitts oscillator and derive the equation for oscillation frequency.
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Classify power amplifiers based on collector current waveforms and conduction angle. Draw the circuit diagram of class A series fed power amplifier and prove that the conversion efficiency is 50% by using transformer coupling.
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Discuss the drawback of class B amplifier and how do you overcome using Class AB amplifier.
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Draw an RC differentiator circuit. Give the conditions for an RC circuit to behave as a differentiator.
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Sketch the response of RC High pass circuit for exponential input and Ramp input and derive the output equations for the above inputs.
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Explain the operation of a negative peak clamper circuit with its diagram.
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Distinguish between the Diode Clippers and Transistor Clippers with their merits.
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Explain with neat sketches the working of a Diode and Transistor as switches.
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Describe the switching times of BJT by considering the charge distribution across the base region.
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