Question Paper: Analog Electronics Question Paper - Dec 18 - Electrical And Electronics (Semester 3) - Jawaharlal Nehru Technological University (JNTUH)
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## Analog Electronics - Dec 18

### Electrical And Electronics (Semester 3)

Total marks: 75
Total time: 3 Hours
INSTRUCTIONS
(1) Each question has 10 marks and may have a,b,c as sub questions.
(2) 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.
(3) Draw neat diagrams wherever necessary.

1.a. What are the types of distortion in amplifiers.
(2 marks) 00

1.b. Classify the amplifiers according to the method of coupling.
(3 marks) 00

1.c. Why the H parameter model is not suitable to analyse transistor at high frequencies.
(2 marks) 00

1.d. What are the elements in the Hybrid '$\small \Pi$' model?
(3 marks) 00

1.e. What is cascade amplifier?
(2 marks) 00

1.f. state the advantages and disadvantages of the source follower.
(3 marks) 00

1.g. What is meant by positive and negative feedback?
(2 marks) 00

1.h. State the Barkhausen criterion for oscillations.
(3 marks) 00

1.i. What are the requirements of a tuned amplifier?
(2 marks) 00

1.j. Give the definition of power amplifier. Also list the types in it based on location of Q point.
(3 marks) 00

PART-B

2 Draw the h parameter equivalent circuit for a typical emitter amplifier and derive expression for Ai, Av, Ri, and Ro.
(10 marks) 00

3 Draw simplified h parameter equivalent circuit and calculate Ai. Av. Avs, Ri, and Ro for the cascade circuit shown in figure 1, Assume that transistors are identical with $h_{fe} = 10, h_{ie} = 2k \small \Omega, h_{re} = h_{oe} = 0$

(10 marks) 00

4.a. Derive an expression for current gain with resistive load.
(5 marks) 00

4.b. The hybrid - $\small \Pi$ parameters of the transistor used in the circuit shown in figure 2 are $g_{m} = 50 mA/V ,r_{be} = 1 k \small \Omega , r_{bc} = 4 M\small \Omega, r_{ce} = 80 k \small \Omega, C_{c} = r pF, C_{e} = 100 pF and r_{bb`} = 100 \small \Omega$, find i) upper 3 dB frequency of current gain ii) the Magnitude of voltage gain at $A_{vs} = V_{o} / V_{s}$ at frequency of part i)

(5 marks) 00

OR

5.a. A single stage CE amplifier is measured to have a voltage gain bandwidth fH of 5 MHz, with $R_{L} = 500 \small \Omega$. Assume $h_{fe} = 100, g_{m} = 100 mA/V, r_{bb} = 100 \small \Omega, C_{c} = 1 pF and f_{T} = 400 MHz$. i) find the value of source resistance that give the required bandwidth . ii) with the value of Rs found in i) , find the mid band voltage gain $V_{o}/V_{s}$.
(5 marks) 00

5.b. In hybrid 'pi' model of a transistor at high frequencies, show that the $g_{m}$ is proportional to the collector current.
(5 marks) 00

6.a. Discuss the input and output characteristics of a folded cascade amplifier with NMOS input.
(5 marks) 00

6.b. Derive expression for $A_{v}$ , and $R_{o}$ for common gate amplifier.
(5 marks) 00

OR

7.a. Draw and explain the CS stage with diode connected load.
(5 marks) 00

7.b. Discuss the MOSFET characteristics in depletion mode.
(5 marks) 00

8.a. Show that for a current series feedback amplifier the input and output resistances are increased by a factor if $(1 + A \small \beta)$ with feedback.
(5 marks) 00

8.b. Identify the topology of feedback in the circuit of figure 3 giving Justification . Two transistors are identical with $h_{ie} =2k$ and $h_{fe} = 100.$ Calculate i)$R_{if}$ ii)$A_{if}$ iii)$A_{vf}$

(5 marks) 00

9.a. Explain the principle of operation of the wein bridge oscillator.
(5 marks) 00

9.b. Mention the features and advantages of the crystal oscillator.
(5 marks) 00

10.a. Show that the transformer coupled class A amplifier maximum efficiency is 50%.
(5 marks) 00

10.b. Compare the push-pull class B and complementary symmetry class B amplifier.
(5 marks) 00

OR

11.a. A tuned amplifier is required to have a voltage Gian of 30 at 10.7MHz with 200 KHz BW, An FET with $g_{m}= 5 mA/V$ and $r_{d} = 100 k \small \Omega$ is available . Calculate the values of tank circuit elements.
(5 marks) 00

11.b. Draw and explain the frequency response of tuned amplifier.
(5 marks) 00

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