JNTU
JNTU B.Tech II ELECTRONIC CIRCUIT ANALYSIS Previous Question Paper (December - 2018 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
How the amplifiers are classified?
Answer
Amplifiers are classified based on the input signal frequency (Audio, Radio, Video), the method of operation (Class A, B, AB, C), the coupling method (RC, Transformer, Direct), and the number of stages (Single-stage, Multi-stage).
State and prove Miller’s theorem.
Answer
Miller's theorem states that an impedance Z connected between two nodes with a voltage gain A can be replaced by two impedances connected from each node to ground. The input impedance is Z/(1-A) and the output impedance is Z/(1-1/A). Proof: Given nodes 1 and 2 with voltages V1 and V2, where V2 = AV1, the current through Z is I = (V1-V2)/Z = V1(1-A)/Z. The input impedance is Z_in = V1/I = Z/(1-A). Similarly, for the output side, I_out = (V2-V1)/Z = V2(1-1/A)/Z, so Z_out = V2/I_out = Z/(1-1/A).
What is gain bandwidth product?
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Why emitter bypass capacitor is needed?
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How the stability of amplifier will affect by negative feedback amplifier?
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State the necessary conditions for oscillator.
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Define conversion efficiency of power amplifiers.
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How is crossover distortion eliminated in class AB amplifier?
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What are the applications of tuned amplifier?
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What is the coefficient coupling in a double tuned amplifier?
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Part B - Unit 1
Draw the equivalent circuit for the CE and CC configurations subject to the restriction that RL = 0. Show that the input impedance of the two circuits are identical.
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The transistor amplifier shown in figure 1 uses a transistor with typical h parameter values. Calculate Ai, AV, AVs, Ro and Ri.
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Draw the circuit diagram of Darlington emitter follower and derive the expression for input impedance.
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Explain the working of cascade amplifier with neat circuit diagram.
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Part B - Unit 2
Draw the hybrid π equivalent circuit of a transistor in CE configuration and explain the various parameters in it.
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A transistor biased at 5mA, 10V, hie = 600Ω, hfe=100, CC=3pF and current gain of 10 at a frequency of 20MHz. Find β cut off frequency, gain band width product, Ce, rb′e and rbb′.
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Calculate the voltage gain of the FET amplifier shown in the figure 2. Assuming blocking capacitor to be large. gm=4mA/V and rd = 5K.
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Sketch the small signal model of a CD FET amplifier and derive equation for the voltage gain.
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Part B - Unit 3
Draw the negative feedback topologies and explain them.
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An open loop amplifier has a midband gain of 500 and a pass band from 50Hz to 50KHz. Find voltage gain and cut off frequencies if 10% of output voltage is fed back.
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Derive an expression for frequency of oscillations of a wien bridge oscillator using transistor.
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Part B - Unit 4
Explain how the efficiency of the class A power amplifier is improved by the transformer coupled amplifier configuration?
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A transformer coupled class A power amplifier supplies the power to an 80Ω load connected across the secondary of a transformer having turns ratio of 5:1. If Ic = 120mA, find maximum output power?
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Derive an equation of output power of a class B power amplifier.
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Draw the circuit diagram of complementary symmetry class B pushpull amplifier and explain its working.
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Part B - Unit 5
Why is double tuning employed in tuned amplifier? What are the advantages of it?
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What are applications of stagger tuned amplifier?
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What are the high frequency limitations of a tuned amplifier? How are they eliminated?
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How is the bandwidth of tuned amplifier improved? Draw such a circuit and explain its working.
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