EC2251 Electronic Circuits B.E Model Question Paper : aalimec.ac.in

Name of the College : Aalim Muhammed Salegh College of Engineering
University : Anna University
Department : Electronics and Communication Engineering
Subject Code/Name : EC2251 Electronic Circuits – II
Degree : B.E
Year : II
Semester : IV
Document Type : Model Question Paper
Website : aalimec.ac.in

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https://www.pdfquestion.in/uploads/aa…II_MODEL_i.pdf
https://www.pdfquestion.in/uploads/aa…I_MODEL_ii.pdf
https://www.pdfquestion.in/uploads/aa…_MODEL_iii.pdf

AALIMEC Electronic Circuits Model Question Paper

B.E./B.Tech. Degree Model Examination
Fourth Semester -Ec2251 — Electronic Circuits – II
Time: Three hours
Maximum:100 Marks

Related : Aalim Muhammed Salegh College of Engineering EC2255 Control Systems B.E Model Question Paper : www.pdfquestion.in/1576.html

Paper – I

Part A : (10 × 2 = 20 Marks)
1. What is the impact of negative feedback on noise in circuits?
2. Define sensitivity and de-sensitivity of feedback amplifiers.
3. Mention two essential conditions for a circuit t o maintain oscillations.

4. In a RC phase shift oscillator, if R1=R2=R3= 200 KO and C1=C2=C3=100pF find the frequency of the oscillator.
5. Define tuned amplifier.
6. Define the term unloaded Q factor.
7. Give two applications of Bistable multivibrator.
8. If an Astable multivibrator has C1=C2=1000pf and R1=R2=20 KO, Calculate the frequency of oscillation.
9. Mention any two applications of blocking oscillator.
10. What is the function of time base circuit?

Part B : (5 × 16 = 80 Marks)
11. (a) (i) Explain impact of negative feedback on bandwidth, distortion, Input Impedance and Output Impedance of a circuit. (8)
(ii) An amplifier has a mid-frequency gain of 100 and a bandwidth of 200 KHz. (1) What will be the new bandwidth and gain, if 5% negative feedback is introduced? (2) What should be the amount of feedback, if the bandwidth is to be restricted to 1 MHz? (8)
Or
(b) (i) Explain voltage shunt feedback and derive the input and output impedance. (8)
(ii) Explain Nyquist criterion to analyse the stability of feedback amplifiers. (8)

12. (a) Explain RC phase oscillator and derive its frequency of oscillation. (16)
Or
(b) Explain Wien Bridge oscillator and derive its frequency of oscillation. (16)

13. (a) Describe the single tuned amplifier with neat diagram (16)
Or
(b) (i) Explain class C tuned amplifier and derive its efficiency. (10)
(ii) Explain Hazeltine Neutralization Method. (6)

14. (a) what is the response of low pass RC circuit for sinusoidal, step, pulse, square wave and ramp inputs (16)
Or
(b) Explain Astable multi vibrator with neat sketch (16)

15. (a) (i) Explain about monostable blocking oscillator with base timing. (8)
(ii) Explain the working of UJT saw tooth generator and derive its frequency (8)
Or
(b) (i) Explain any one type of Current-Time Base Circuit (8)
(ii) How does an Astable circuit act as a free running blocking oscillator? Draw the circuit and explain (8)

Paper – II

Answer ALL Questions
PART A : (10 × 2 = 20 Marks)
1. What is ‘return ratio’ of a feedback amplier?
2. State t he effect on output resistance and on input resistance of amplier when current shunt feedback is employed.
3. A Wein bridge oscillator is used for operations at 9 kHz. If the value o f the resistance R is 100 kO, what is the value of C required?
4. A tuned collector oscillator in a radio receiver has a fixed inductance of 60 µH and has to be tunable over the frequency band of 400 KHz to 1200 KHz. Find the range of variable capacitor to be used.
5. What is t he effect o f cascading n stages of identical single tuned ampliers (synchronously tuned) on the overall 3 dB bandwidth?
6. What is narrow band neutralization?
7. What is meant by clipper circuit?
8. What are the applications of Bistable multivibrator?
9. What are the applications of Blocking oscillator?
10. Sketch and define the `slope error’ of a voltage sweep waveform.

Part B : (5 x 16 = 80 marks)
11. (a) (i) Sketch the block diagram of a feedback amplier and derive the expressions for gain (1) with positive feedback and (2) with negative feedback. State the advantages of negative feedback. (6)
(ii) An amplier, without feedback, has a voltage gain of 400, lower cut-of frequency f1= 50 Hz, upper cut-of frequency f2= 200 KHz and a distortion of 10%.Determine the amplier voltage gain, lower cut-of frequency and upper cut-of frequency and distortion, when a negative feedback is applied with feedback ratio of 0.01. (5)
(iii) An amplier, with feedback, has voltage gain of 100. When the gain without feedback changes by 20% and the gain with feedback should not vary more than 2%. If so, determine the values of open loop Gain A and feedback ratio ß. (5) OR

11. (b) (i) Draw the circuits of voltage shunt and current series feedback ampliers and derive the expressions for input impedance Rif . (10)
(ii) Discuss Nyquist criterion for stability of feedback ampliers, with the help of Nyquist plot and Bode plot. (6)

12. (a) (i) Sketch the basic block diagram of an oscillator an d explain how it works. If the gain of the amplifier is A and the feedback factor is ß , sketch the output waveforms for t he three cases (1) |Aß| > 1, (2) |Aß| = 1 and (3) |Aß| < 1. Derive the conditions of sustained oscillations. (10)
(ii) Make a table of comparison of RC phase shift oscillator and Wien-bridge oscillator bringing out the similarities and differences. (6)
OR
12. (b) (i) Explain the working of a Colpitts oscillator with a neat circuit diagram and derive the frequency of oscillation. (8)
(ii) In a Colpitt’s oscillator, the value of the inductor and capacitors in the tank circuit are L = 40 mH, C1 = 100 pF and C2 = 500 pF. (8)
(1) Find t he frequency o f oscillation.
(2) If the output voltage is 10 V, and the feedback voltage at the input side of the amplifier.
(3) Find the minimum gain, if the frequency is changed by charging `L’ alone.
(4) Find the value of C1for a gain of 10 if C2 is kept constant as 500 pF. Also and the resulting new frequency.