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Tuesday, 24 July 2012

Electronic Circuits II question bank free download


 Anna University
EC2251: ELECTRONIC CIRCUITS II
SEM / YEAR: IV/ II
QUESTION BANK – 2012 Edition
UNIT I
FEEDBACK AMPLIFIERS

PART-A
1. Define positive and negative feedback.
2. Define loop gain.
3. List the characteristics of negative feedback amplifiers.
4. Addition of negative feedback to an amplifier reduces its voltage gain from 300 to 60.Determine the feedback factor.
5. What are the different classifications of negative feedback amplifier?
6. How negative feedback causes reduction in noise in amplifiers?
7. Draw the equivalent circuit of a transconductance amplifier.
8. Derive using a block diagram the closed loop forward transfer ratio Af of a feedback system.
9. If an amplifier has a gain of 400and feedback ratio is 0.1,find the gain with negative feedback
10. Compare the input and output resistance for a voltage and current shunt feedback amplifier.
11. Draw a block diagram of voltage shunt feedback feedback amplifier and give its input and output resistance.
12. What are the disadvantages of negative feedback?
13. How negative feedback reduces distortion in an amplifier?
14. Define feedback factor.
15. What are the advantages of negative feedback in amplifier.
16. Define desensitivity of transfer gain.
17. Determine the gain of an amplifier with feedback,when the open loop gain is 200 and the feedback factor is 0.2.
18. Determine the gain with feedback for the amplifier with the open loop and feedback factor 0.1.
19. Identify the type of feedback of the circuit shown:
PART-B
1. Draw the circuit of a current series feedback amplifier and explain . Derive expressions for input and output impedance.
How does it improve the stability of the amplifier. (16)
2. (i) Draw the block diagrams of the four possible feedback topologies and explain. (6)
(ii) Prove that the bandwidth of the amplifier increases with negative feedback. (10)
3. (i) Show how negative feedback reduces gain of an amplifier. (8)
(ii) Explain the effect of negative feedback on the input resistances for a voltage shunt feedback amplifier. (8)
4. Explain the working of voltage series feedback amplifier with circuit diagram and small signal equivalent circuit. Derive the expressions for voltage gain, input impedance and output impedance. (16)
5. (i) Draw the circuit diagram and equivalent circuit for current shunt feedback amplifier and derive the expression for total voltage gain. (10)
(ii) what are the different performance measures of feedback amplifiers? Discuss each in brief. (6)
6. (i)What is the effect of negative feedback on the bandwidth and distortion of an amplifier. (10)
(ii) A negative feedback is used to reduce the noise from an amplifier by 80%.Waht must be the percentage negative feedback to accomplish this if the amplifier voltage gain is 100? (6)
7. Draw the circuit of an emitter follower. Identify the type of negative feedback.calculate the gain, input and output resistance with and without feedback. (16)
8. Describe with necessary derivations, discuss the effects of negative feedback amplifier. (16)
9. (i) Discuss the classification of feedback amplifiers with schematic (topology).How is impedance level modified in each type? (8)
(ii) Derive expression for Avf with positive and negative feedback and state condition for stability in negative feedback amplifiers. (8)
UNIT-II
OSCILLATORS
PART A
1. What is oscillator?
2. What are the classifications of Oscillators?
3. What are the factors which affect the frequency stability of an oscillator?
4. Draw the equivalent circuit of a quartz crystal.
5. A wein bridge oscillator is used for operation at 10KHz . If the value of the resistance R is 100 K ohms , what is the value of C required.
6. Define Barhausen Criterion.
7. What are the types of feedback oscillators?
8. What are the conditions for oscillation?
9. Define Piezoelectric effect.
10. Draw the equivalent circuit of crystal oscillator.
11. What is Miller crystal oscillator?
12. State the frequency for RC phase shift oscillator.
13. What is Q factor?
14. What is dissipation factor?
15. Draw the electrical equivalent circuit of crystal and mention the significance of each component.
16. Draw the Miller’s oscillator circuit.
PART B
1. Describe Hartley oscillator with neat circuit diagram . Determine the frequency of oscillations and the oscillation condition for it. (16)
2. Write short notes on
(i)Milter oscillator (8)
(ii) Crystal oscillator (8)
3. (i)Sketch the circuit and explain the operation of a RC phase shift oscillator .Derive the expression for frequency and condition for sustained oscillations for the circuit. (12)
(ii)Explain the need for three RC networks for the circuit functioning. (4)
4. With a neat circuit diagram ,explain the operation of a transistor pierce crystal oscillator. (16)
5. Explain the principle of operation of a wein bridge oscillator. (16)
6. Draw the amplitude and phase conditions that are to be satisfied in LC oscillators using pi network.Hence obtain the frequency of oscillator of a Hartley oscillator. (16)
7. (i)With circuit diagram drive an expression for frequency of oscillation of a Clapp oscillator .Explain how Barhausen conditions are satisfied. (8)
(ii) Bring out the advantages of Clapp oscillator over Colpitt oscillator. (8)
1. What are the advantages of tuned amplifiers?
2. What are the disadvantages of tuned amplifiers?
3. What is neutralization?
4. What are double tuned amplifiers?
5. What is a stagger tuned amplifier?
UNIT III
TUNED AMPLIFIERS
PART A
6. What are the advantages of double tuned over single tuned?
7. What are the different types of neutralization?
8. What is rice neutralization?
9. What is unloaded Q?
10. What are the different coil losses?
11. A tuned amplifier is designed to receive A.M. broad cast of speech signal at 650kHz. What is needed Q for amplifier?
12. Why neutralization is used in tuned amplifiers?
PART B
1. (i)Explain the effect of changing Q of the coil used in tank circuit on its bandwidth. (8)
(ii) Derive the equation for 3 dB bandwidth of capacitance coupled single tuned amplifier. (8)
2. (i)What is stagger tuned amplifier? Explain its working. (8)
(ii)Write brief notes on Hazeltine neutralization.
3. Define Quality factor.Obtain the quality factor for a parallel resonant circuit. (16)
4. (i)Explain the working and frequency response of a single tuned amplifier circuit. (12)
(ii)What are synchronous and stagger tuned amplifier circuits. (4)
5. With circuit diagram and waveforms explain the operation of a Schmitt trigger circuit using two transistors for a sinusoidal input. (16)
6. (i)Draw a class c tuned amplifier and drive its efficiency. (8)
(ii)Describe any one method of neutralization used in tuned amplifier. (8)
7. (i)Draw the single tuned amplifier and explain the frequency response. (6)
(ii)Drive the expression for its gain and cutoff frequency (6)
(iii)What is meant by synchronous tuning of tuned amplifier. (4)

UNIT-IV
WAVE SHAPING AND MULTIVIBRATOR CIRCUITS
PART A
1. What is multivibrator?
2. Name the types of Multivibrators?
3. How many stable states do bistable Multivibrator have?
4. What are the applications of bistable Multivibrator?
5. What are the different names of bistable Multivibrator?
6. Why is monostable Multivibrator called gatting circuit?
7. Why is monostable Multivibrator called delay circuit?
8. What is the main characteristics of Astable Multivibrator?
9. What is the other name of Astable Multivibrator- why is it called so?
10. What are the two types of transister bistable Multivibrator?
11. How are the values R1, R2 and VBB chosen in bistable Multivibrator?
12. What is self biased Multivibrator?
13. What are the other names of speed up capacitors?
14. Define transition time.
15. Define resolving time.
16. Define gate width.
17. What are the advantages of monostable Multivibrator?
18. What are the applications of astable Multivibtrator?
19. What is a complementary Multivibrator?
20. What is the important application of Schmitt trigger?
PART B
1. (i)Explain the working principle of complementary collector coupled astable multivibrator. (8)
(ii)With neat circuit diagram, explain the operation of bistable multivibrator. (8)
2. (i)Describe the different triggering methods used for multivibrator circuits. (8)
(ii)Draw and explain Schmitt trigger circuit and also draw the its waveform. (8)
3. (i)Draw the circuit of a collector coupled transistor monostable multivibrator.Sketch the waveforms at base and collector for each transistor when the circuit is trigerred and explain its working. (10)
(ii)Explain circuits used to trigger a transistor monostable multivibrator circuit. (6)
4. Design a Schmitt trigger circuit for Vcc=10 V;UTP=5 V;LTP=3V.Assume hfe=100 and Ic=1 mA. (16)
5. Design a monostable multivibrator for the following specifications:Vcc=10 V;Vbb=6V;Ic=1 mA;duration of output pulse=14 sec;hfe min=100;Icbo=0;Vbe=-0.5 V. (16)
6. (i)Explain the working of emitter coupled astable multivibrator with a circuit diagram and derive for its frequency. (8)
(ii)Design the collector coupled astable multivibrator using Vcc=20V and Ic sat= 3 mA to generate a pulse wave at f=2 kHz with 70% duty cycle. (8)

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EC 2305 Transmission Lines and Waveguides question bank download


EC2305: TRANSMISSION LINES & WAVE GUIDES SEM / YEAR: V / III
                                    (REGULATION 2004)

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

QUESTION BANK

SUBJECT NAME : TRANSMISSION LINES & WAVE GUIDES

UNIT I - TRANSMISSION LINE THEORY
PART – A
All questions – Two Marks:
  1. What is group velocity?
  2. What is patch loading?
  3. What do you understand by loading of transmission lines?
  4. Define Characteristic impedance?
  5. What is frequency distortion?
  6. Calculate the load reflection coefficient of open and short circuited lines?
  7. Calculate the characteristic impedance for the following line parameters
  8. R = 10.4 ohms /km L = 0.00367 H/km
  9. C = 0.00835μf /km G = 10.8x10-6 mhos /km
  10. Define phase distortion?
  11. Write the equation for the input impedance of a TL?
  12. Define propagation constant?
  13. Define wavelength?
  14. Give the input impedance of a open and short circuit line?
  15. Define reflection factor?
  16. Define reflection loss?
  17. What is meant by reflection co – efficient?
  18. State the properties of infinite line?
  19.  Write the condition for a distortion less line?
  20.  When does reflection take place on a TL?
  21.  What is transfer impedance? State its expression?
  22.  What is difference between lumped and distributed parameters?
  23.  Draw the equivalent circuit of a TL?
  24.  Write the Campbell’s formula for propagation constant of a loaded line?
  25.  What is the need for loading?

PART – B
  1. Obtain the general solution of Transmission line? (16)
  2. Explain about waveform distortion and distortion less line condition? (16)
  3. Explain about reflection loss? (16)
  4. Discuss in details about inductance loading of telephone cables and derive theattenuation constant (_) and phase constant (_) and velocity of signal transmission(v) for the uniformly loaded cable? (16)
  5. Derive the equation of attenuation constant and phase constant of TL in terms of R,L, C, G? (16)
  6. Explain in details about the reflection on a line not terminated in its
characteristic impedance (z0)? (16)
  1. Explain in following terms (16)
    1. Reflection factor (ii) Reflection loss
    2. Return loss
  2. Explain about physical significance of TL? (16)
  3. Derive the equation for transfer impedance? (16)
  4. Derive the expression for input impedance of lossless line? (16)
  5. Explain about telephone cable? (16)
  6. Explain about different type of TL? (16)




UNIT II - THE LINE AT RADIO FREQUENCIES

PART – A
All questions – Two Marks:
  1. Name few applications of half – wave line?
  2. Find the VSWR and reflection co – efficient of a perfectly matched line with no reflection from load?
  3. Explain the use of quarter wave line for impedance matching?
  4. What is the need for stub matching in transmission lines?
  5. Why do standing waves exist on TL?
  6. Define Node and antinodes?
  7. What are constant S circles?
  8. What are the advantages of double stub matching over single stub matching?
  9. Derive the relationship between standing wave ratio and reflection co – efficient?
  10. Write the expression for the characteristic impedance Ro’ of the matching quarter –wave section of the line?
  11. Give the applications of smith chart?
  12. Define standing wave ratio?
  13. Give the analytical expression for input impedance of dissipation less line?
  14. Design a quarter wave transformers to match a load of 200 _ to a source resistance of 500 _. The operating frequency is 200 MHz?
  15. Define skin effect?
  16. What is zero dissipation line?
  17. Mention the assumptions of radio frequency lines?
  18. Distinguish between single stub matching and double stub matching?
  19. Write down the expression to determine the length of the stub?
  20. Write down the expression to determine the position of the stub?


PART – B
  1. Explain about half wave transformer? (8)
  2. Application of smith chart? (8)
  3. Explain about voltage and current waveform of dissipation less line? (16)
  4. Derive the expression for the input impedance of the dissipation less line and theexpression for the input impedance of a quarter wave line. Also discuss the applicationof quarter wave line? (16)
  1. Explain single stub matching on a transmission line and derive the expression and the length of the stub used for matching on a line? (16)
  2. Design a single stub match for a load of 150+j225 ohms for a 75 ohms line at 500 MHz using smith chart? (16)
  3. A 30 m long lossless transmission line with characteristic impedance (zo) of 50 ohm is terminated by a load impedance (ZL) = 60 + j40 ohm. The operating wavelength is 90m. find the input impedance and SWR using smith chart? (16)
  4. Explain double stub matching on a transmission line and derive the expression and thelength of the stub used for matching on a line? (16)
9.  Explain about _ / 8 wave transformer? (16)
    10.  explain about properties of smith chart? (16)


UNIT III - GUIDED WAVES
Part-A
All questions – Two Marks:
  1. Define group velocity?
  2. What are the characteristics of TEM waves?
  3. What is the cut off frequency of TEM wave?
  4. Give the expression that relates phase velocity (Vp), Group velocity (Vg) and free space velocity?
  5. What are TE waves or H waves?
  6. What are TM waves or E waves?
  7. What are guided waves?
  8. What is dominant mode? Give examples?
  9. Write down the expression for cut off wavelength and cut off frequency?
  10. Write down the expression for velocity of propagation?
  11. Define attenuation factor?
  12. Define wave impedance?
  13. Distinguish between TE and TM waves?
  14. Write down the relation between guide wavelengths and cut off wavelength?
  15. Give the expression for the guide wavelength when the wave transmitted in between two parallel plates?
  16. Find the frequency of minimum attenuation foe TM waves?
  17. Give relation between the attenuation factor for TE and TM waves?
  18. Draw a neat sketch showing the variation in the value of attenuation with frequency for TE, TM, and TEM mode between two parallel plates?
  19. Draw a neat sketch showing the variation in the value of wave impedance with frequency for TE, TM, and TEM mode between two parallel plates?








Part-B
  1. Discuss the characteristics of TE and TM waves and also derive the cut off
frequency and phase velocity from the propagation constant? (16)
  1. Derive the expression for the field strength for TE waves between parallel plates propagating in Z direction? (16)
  2. Derive the expression for attenuation of TM waves in between parallel plates?(16)
  3. Derive the expression for attenuation of TE waves in between parallel
  1. Plates? (16)
  1. Derive the expression for the field strength for TM waves between
  1. Parallel plates propagating in Z direction? (16)
  1. Obtain the expression for the field components of an electromagnetic wave propagating between a pair of perfectly conducting planes? (16)
  2. Derive the expression for wave impedance of TE, TM and TEM wave between a pair of perfectly conducting planes? (16)
  3. Explain about transverse electromagnetic waves between a pair of perfectly conducting planes? (16)
  4. Prove that the velocity of propagation? (16)



UNIT IV - RECTANGULAR WAVEGUIDES

Part-A
All questions – Two Marks:
  1. What are the dominant mode and degenerate modes in rectangular wave – guides?
  2. A rectangular wave – guides has the following values l=2.54 cm, b= 1.27 cm waveguide thickness = .0127. Calculate the cut off frequency?
  3. Define wave impedance?
  4. Why TEM mode is not possible for rectangular wave – guides?
  5. Define characteristic impedance?
  6. Define attenuation factor?
  7. Draw a neat sketch showing the variation in the value of attenuation with frequency for TE, TM, and TEM mode for rectangular wave guide?
  1. Draw a neat sketch showing the variation in the value of wave impedance with frequency for TE, TM, and TEM mode for rectangular wave guide?
  2. Write down the expression for cut off wavelength and cut off frequency for rectangular wave guide?
  3. Write down the expression for cut off wavelength and cut off frequency for  TE 10 mode?
  1. Write down the expression for guide wavelength and velocity of propagation for rectangular wave guide?
  2. Write down the expression for attenuation constant for TE 10 mode?
  3. Write down the expression for attenuation constant for TM 11 mode?
  4. What is cut off frequency?
  5. What is dominant mode? Name the dominant mode in TE and TM waves?

Part-B
  1. Derive the field configuration, cut off frequency and velocity of propagation for TM waves in rectangular wave – guides? (16)
  2. Determine the solution of electric and magnetic fields of TE waves guided along rectangular wave – guides? ` (16)
  3. Explain the wave impedance of a rectangular wave – guide and derive the expression for the wave impedance of TE,TM, and TEM mode? (16)
  4. Discuss the characteristics of TE and TM waves and also derive the cut off frequency and phase velocity from the propagation constant? (16)
  5. Derive the expression for attenuation of TE10 waves in rectangular wave guide? (16)
  6. Derive the expression for attenuation of TM 11 waves in rectangular wave guide? (16)
  7. Explain about excitation modes in rectangular wave guide? (16)
  8. Explain about dominant mode in rectangular wave guide? ` 16)
  9. Determine the solution of electric and magnetic fields of TM waves guided along rectangular wave – guides? (16)
  10. Explain about characteristic impedance in rectangular wave guide? (16)
  11. Explain about degenerate mode in rectangular wave guide? (16)


UNIT V - CIRCULAR WAVE GUIDES AND RESONATORS

Part-A
All questions – Two Marks:
  1. What is cavity resonator?
  2. Define the quality factor of the cavity resonator?
  3. Define loaded and un loaded Q cavity resonator?
  4. Give the application of circular wave guide?
  5. Why rectangular or circular cavities can be used as microwave resonators?
  6. Define Bessel’s function?
  7. What is Eigen value?
  8. What is dominant mode of TM and TE waves in circular waveguide?
  9. Write expressions for the Eigen value and cut off wave number for the TE mode?
  10. Write expressions for the Eigen value and cut off wave number for the TM mode?
  11. Expression for the resonant frequency of the rectangular cavity resonator?
  12. Expression for the resonant frequency of the circular cavity resonator?
  13. Expression for the quality factor of the circular cavity resonator?
  14. Expression for the quality factor of the rectangular cavity resonator?
  15. Define cavity tuning?
  16. Define resonant cavity?
  17. Give the application of microwave resonator?





Part-B
  1. Derive the Q-factor of a rectangular cavity resonator? (16)
  2. Derive the TM wave components in circular wave guides using Bessel functions? (16)
  3. What is meant by cavity resonator? Derive the expression for the resonant frequency of the rectangular cavity resonator? (16)
  4. Derive the expression for cut off frequency, phase constant and phase velocity of wave in a circular wave guide? (16)
  5. Derive the expression for the resonant frequency of the circular cavity resonator? (16)
  6. Derive the expression for the resonant frequency of the semi circular cavity resonator? (16)
  7. Derive the TE wave components in circular wave guides using Bessel functions?(16)
  8. Derive the expression for the wave impedance in circular wave guide? (16)
  9. Derive the field strength or equation in cylindrical co – ordinates systems?