JNTU
JNTU B.Tech II ANALOG ELECTRONICS Previous Question Paper (April/May - 2018 - R16)
Note: This question paper contains two parts A and B. 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 and may have a, b, c as sub questions.
Part A
Write the characteristic of CE amplifier.
Answer
The Common Emitter (CE) amplifier is characterized by high voltage gain, high current gain, and moderate input and output impedances. It provides a phase reversal of 180 degrees between the input and output signals.
Discuss the need of Darlington pair circuit.
Answer
The Darlington pair is used to achieve a very high input impedance and a very high overall current gain (β), which is approximately the product of the individual transistor gains. It is essential in applications requiring high current drive capability and minimal loading effect on the preceding stage.
What is meant by gain bandwidth product?
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Short circuit CE current gain of a transistor is 25 at a frequency of 2 MHz. If fβ = 200 kHz calculate fT, hfe and |Ai| at frequency of 10 MHz and 100 MHz.
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State the advantages and disadvantages of cascode stage.
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What is the folded cascode amplifier? Discuss.
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Classify the various negative feedback amplifiers.
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For a phase shift oscillator, the feedback network uses R=6 KΩ and C=1500 pF. The transistorized amplifier used, has a collector resistance of 18 KΩ. Calculate the frequency of oscillation and minimum value of hfe of the transistor.
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What is the use of the heat sink in power amplifiers?
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What is meant by loaded and unloaded Q.
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Part B
Discuss the low frequency response of BJT amplifier and the effect of coupling and bypass capacitors.
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Explain the different coupling schemes used in amplifiers.
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For a two stage amplifier shown in figure 1 calculate (a)Av (b) Avs, (c) Ri (d) Ro. Neglect the effect of all capacitances, Assume that the both the transistors are identical with following parameters. hfe=50, hie=1.1KΩ, hre= 2.5 × 10-4, hoe=24×10-6 A/V.
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For a single stage CE amplifier whose hybrid Π parameters are given below. What value of Rs will give 3 dB frequency fH' which is half the value obtained with Rs=0. Hybrid Π parameters are: gm=50 mA/V, rbb'=100Ω, rb'e=1 KΩ, CC=3 pF, Ce=100 pF.
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A BJT has the following parameters measured at Ic=1 mA, hie=3 KΩ, hfe=100, fT=4 MHz, CC=2pF and Ce=18 pF. Find rb'e, rbb', gm and fH for RL=1 KΩ.
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Prove that hfe = gm rb'e.
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Derive the expression for CE short circuit current gain Ai as a function of frequency.
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Compare the performance of BJT and FET amplifiers.
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Draw and explain the CS amplifier with current source load. Derive an expression for Av.
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Draw and explain the MOS small signal model.
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Discuss the analysis of CD JFET amplifier.
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What are the advantages and disadvantages of negative amplifier in detail?
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For the given circuit shown in figure 2, calculate Rmf, Avf and Rif. The transistors with parameters hie=2 KΩ, hfe=100. Neglect hoe and hre.
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In a colpitt’s oscillator, the values of the inductors and capacitors in the tank circuit are L=40mH, C1=100 pF, C2=500 pF.
- i) Find the frequency of oscillation.
- ii) If the output voltage is 10 V, find the feedback voltage.
- iii) Find the minimum gain, if the frequency is changed by changing ‘L’ alone.
- iv) Find the value of C1, for a gain of 10.
- v) Also find the new frequency of oscillation.
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Compare the RC phase shift and wein bridge oscillators.
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Explain the principle of operation of class C amplifier.
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Design a class B power amplifier to deliver 25 W to a load resistors RL=8 Ω using transformer coupling, Vm=VCC=25 V. Assume reasonable data where ever necessary.
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An RF tuned voltage amplifier using FET with rd=100 KΩ and gm=500μs has tuned circuit, consisting of L=2.5mH and C=200 pF as its load. At its resonant frequency, the circuit offers an equivalent shunt resistance of 100 KΩ. For the amplifier, determine the (i) the resonant gain (ii) the effective Q and (iii) the bandwidth.
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Draw and explain the double tuned amplifier with the help of the frequency response.
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