SEMESTER: IV SUBJECT: ELECTRONIC CIRCUITS-I QB

VINAYAKA MISSIONS UNIVERSITY, SALEM

V.M.K.V. ENGINEERING COLLEGE

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING 

QUESTION BANK 

BRANCH: ELECTRONICS AND COMMUNICATION ENGINEERING

SEMESTER: IV

SUBJECT: ELECTRONIC CIRCUITS-I

ELECTRONIC CIRCUITS- I

                                                                                                 

 1. BASIC STABILITY AND DEVICE STABILIZATION                                     9

Biasing circuits for BJT, DC and AC Load lines, Stability factor analysis, Temperature  compensation methods, biasing circuits for FET's and MOSFET's.         

                                                                        

 2. SMALL SIGNAL LOW FREQUENCY ANALYSIS AND DESIGN                9

Transistor, FET and MOSFET Amplifiers, Equivalent circuit, input and output characteristics, calculation of  midband gain, input and output impedance of various amplifiers, cascode amplifier, Darlington Bootstrapping,  Differential amplifier, CMRR  measurement, Use of current source in Emitter.           

                                   

 3.  LARGE SIGNAL AMPLIFIERS                                                                           9

Class A, AB, B, C and D type of operation, efficiency of Class A amplifier with resistive and transformer coupled load, efficiency of  Class B, Complementry Symmetry amplifiers, MOSFET Power amplifiers, Thermal  stability of Power amplifiers, heat sink design.    

                                                                     

 4. FREQUENCY RESPONSE OF AMPLIFIERS AND ANALYSIS USING SPICE     

    9

High frequency equivalent circuits for BJT and FET amplifiers, Calculation of Lower and Higher cutoff frequencies, Bode plot of  frequency response, relation bandwidth and rise time, Compensation to improve the low frequency and high frequency response of amplifiers, HF amplifiers, Video amplifiers, Optocouplers, BJT modelling, The sinusoidal and Pulse source modelling, Analysis of CE Amplifier  using  SPICE.              

              

 5. RECTIFIERS AND POWER SUPPLIES                                                           9

Half and Full wave rectifiers, Ripple factor calculation for C, L, L-C and -SYMBOL 112f "Symbol" filters,  Switch mode power supplies, Linear electronic voltage regulators, Power control using SCR.                                

                                                                                                                         TOTAL HOURS: 45

TEXT BOOKS:   

                                                                                                     

1.         Millman J. and Halkias C.C., " Integrated Electronics ", McGraw Hill.    

                                      

REFERENCES:                                                                                                         

1.         David A.Bell, " Electronic Devices and Circuits ",  Prentice Hall of India, 1998.                               

2.         Donal L. Schilling Charles Beloue, " Electronic Circuits ", Third Edition, 1989.                                

                                                      

UNIT-I

PART-A

1. Why do we choose q point at the center of the load line?
2. Name the two techniques used in the stability of the q point .explain.
3. Give the expression for stability factor.
4. List out the different types of biasing.
5. What do you meant by thermal runway?
6. Why the transistor is called a current controlled device?
7. Define current amplification factor?
8. What are the requirements for biasing circuits?
9. Draw a collector feedback bias circuit.
10. When does a transistor act as a switch?
11. What is operating point?
12. Define saturation point and cutoff points.
13. Draw the amplifier output waveform, for Q point shifted towards the saturation point.
14. What is meant by faithful amplification?
15. Define active region.
16. What are the factors affecting the stability of Q point?
17. Draw the amplifier output waveform, for Q point shifted towards the cutoff point.
18. How to draw the d.c. load line.
19. State Thevenin’s theorem.
20. Draw the circuit diagram of fixed bias circuit.
21. How temperature affects the stability factor.
22. Mention the devices that are used in bias compensation.
23. How thermistor is used for bias compensation.
24. Define d.c load line.
25. Find the upper and lower ends of d.c load line, for the Vcc= +20 Volts, R_C=300 Ωs.

                                                            PART B

1. Briefly explain the reasons for keeping the operating point of a transistor as fixed
2. Explain fixed bias and emitter feedback bias
3. Explain voltage divider biasing and derive the expression for its stability factor
4. Explain collector feed back bias and derive the stability factor
5. Compare the stability of various biasing circuits
6. How would you provide temperature compensation for the variation of V_BE and stabilization of the operating point?
7. Can the value of stability factor be less than unity? Explain it briefly.
8. What are the biasing schemes available to achieve the required bias in a junction Field effect transistor(JFET)? Explain any one of the biasing schemes.
9. How do you set a Q-Point in a self biased JFET?
10. Explain in detail about the Biasing of Enhancement and depletion type MOSFET.

             

UNIT-2

PART-A

1. Give the applications of Common Base amplifier.
2. Give the characteristics of Common Emitter amplifier.
3. What are the applications of Common Collector amplifier?
4. Write the procedure for A.C. analysis.
5. What is the action of bypass capacitor in CE amplifier?
6. List out the characteristics of CC amplifier.
7. Draw the AC equivalent circuit of Common Base transistor.
8. Which amplifier is called swamped amplifier, why?
9. Give the applications of CC amplifier.
10. Draw the DC equivalent circuit of Common emitter transistor.
11. What is cascode amplifier?
12. What is the advantage of Darlington amplifier?
13. State Millers Theorem.
14. What is differential amplifier?
15. Draw small signal low-frequency FET model.
16. What is CMRR?
17. A certain JFET has g_m = 4mS, with external drain resistance of 1.5KΩ. Find the value of ideal voltage gain.
18. What is the use of Emitter bypass capacitor?
19. Write the procedure for D.C. analysis.
20. Draw emitter follower circuit diagram.
21. Why common drain configuration is called source follower?
22. A FET source follower has g_m of 2mƱ and r_d of 50KΩ. If the source resistance R_S is 1KΩ, find output resistance of the amplifier.
23. Draw small signal high-frequency FET model.
24. A JFET amplifier has g_m is 2.5mA/V and r_d is 500KΩ and load resistance is 10KΩ. Find the value of voltage gain.
25. Mention the advantages and disadvantages of direct coupled amplifier.

PART B

1.      With a neat circuit diagram, explain the working of a transistor amplifier.

2.      Explain the Operation of Common Emitter amplifier and explain the effect of feedback resistor and bypass capacitor.

3.      With a neat circuit diagram, explain the working of a transistor amplifier in which phase inversion of the input signal does not take place. Obtain the expression for input resistance for such an amplifier.

4.      Draw the circuit diagram of common base amplifier and drive expression for current gain and voltage gain.

5.      Draw neatly the circuit diagram of a common source JFET amplifier and explain its working.

6.      What is the effect of external source resistance on the voltage gain of a common source amplifier? Explain with necessary derivation.

7.      Explain the parameters of Darlington amplifier..

8.      Explain the parameters of Cascode amplifier.

9.      Explain the working of Emitter follower and show that the gain of this amplifier is equal to unity.

10.  Explain the operation Differential amplifier.

UNIT-3

PART-A

1. What is the power dissipation and maximum efficiency of class A-amplifier?
2. What is class C power amplifier? Give one application.
3. Define class B amplifier.
4. Define class AB amplifier.
5. How do class A operations take place?
6. Define class AB and class C modes of operation.
7. State the merits of push pull amplifiers.
8. What is power amplifier?
9. What are the basic blocks of PA system?
10. What are the two types of distortion occurs in power amplifiers?
11. How does impedance matching  takes place?
12. How does the instantaneous output voltage become higher than Vcc?
13. How to avoid core saturation?
14. Why is the name push-pull amplifier?
15. What is the advantages and disadvantages of Class B amplifier?
16. What is the derating power amplifier?
17. What is the advantages of using the output transformer for Class A amplifier?
18. What are the types Class A amplifier?
19. State the types of distortions in amplifier?
20. Why is it not possible to use the h-parameter for the analysis of power amplifier?
21. Classify the power amplifiers based on the position of Q point on the ac load line.
22. Why is the efficiency of class A amplifier is the lowest of all the power amplifiers/
23. What are the types of Class B amplifiers?
24. What is the crossover distortion ?how it can be eliminated/
25. What is the configuration used in complementary symmetry power amplifiers? How does it help?

PART B

1.      i.) What is the difference between voltage amplifier and power amplifier? Explain in detail.

ii.) Why a power amplifier is called a large signal amplifier? Explain it briefly.

2.      How do you classify the power amplifier? With the help of suitable sketches or otherwise compare class-A, class-B and class-C amplifiers.

3.      Explain the Operation of  CLASS A amplifier.

4.      Explain the Operation of  Transformer coupled CLASS A amplifier.

5.      Explain the Operation of  CLASS B amplifier and show that the maximum collector efficiency of class-B amplifier is 78.6%..

6.      Explain the Operation of  CLASS C amplifier.

7.      Explain the Operation of CLASS B Push-Pull amplifier and drive an expression for its efficiency.

8.      What is Distortion? Explain the types of Distortions in power amplifier in detail.

9.      Explain in detail about the MOSFET power is pliers and explain in detail about the Thermal stability and Heat sink.

10.  Explain the working of class-AB amplifier in detail with a neat diagram. 

UNIT-4

PART-A

1. Draw the high frequency equivalent circuit of BJT.
2. Draw the high frequency equivalent circuit of FET.
3. Define Bode plot.
4. Define Bandwidth.
5. Define rise time.
6. Define Opto-couplers.
7. What is video amplifier?
8. What is compensation?
9. What is HF amplifier?
10. What is junction Capacitance?
11. Write the significance of frequency response.
12. What are the different regions in frequency response?
13. How to plot the frequency response?
14. Define upper cutoff  frequency.
15. Define lower cutoff frequency.
16. Why does amplifier gain reduce?
17. How to develop equivalent circuits of the amplifier in different frequency ranges?
18. Why the gain roll off is at -20 dB/decade?
19. What are the factors responsible for reduction in gain at low frequencies?
20.  What are the factors responsible for reduction in gain at high frequencies?
21. What do you mean by the half power or 3 dB frequencies?
22. Define f_T.
23. What is the relationship between bandwidth and rise time?
24. What does rise time indicate ? how is it upper 3 dB frequency?
25. What are the high frequency effects?

PART B

1.      What is meant by the term frequency response of an amplifier? Explain the procedure to plot the same.

2.      Explain the effect of coupling and bypass capacitors on the bandwidth.

3.      State and explain various resistances in the hybrid π model.

4.      With suitable diagram explain the high frequency analysis of BJT.

5.      Derive the expression for higher cut off frequency and lower cut off frequency of a BJT amplifier.

6.      Explain High frequency common source amplifier with necessary diagrams.

7.      Discuss about the Compensation techniques to improve the low frequency and high frequency response of amplifiers.

8.      Derive the expression for Bandwidth and Rise time.

9.      Explain Video amplifier.

10. Explain HF amplifier.

UNIT-V

PART-A

1. What are the types of rectifiers?

2.      What are the filters used in rectifier circuits?

3. How many diodes are used in various types of rectifiers?

4.      What are the peak inverse voltages of various types of rectifiers?

5.       What is the ripple factor for various type of rectifier?

6.      What is the advantage of LC filters in comparing with other filters?

7.      Which type of filter is called choke filter?

8.      Define ripple factor and rectification efficiency of a rectifier.

9.      What the efficiency is of varies types of rectifiers?

10.  Define RMS value.

11.  Why the name half wave rectifier?

12.  Why does the output voltage change with change in I_L?

13.  What are the important performance parameters of a half wave rectifier?

14.  Define rectifier.

15.  Define TUF.

16.  Write the advantages and disadvantages of Full wave rectifier.

17.  Write the advantages of bridge rectifier.

18.   What are the important specifications of rectifiers?

19.  How to reduce the ripple factor?

20.  What is a filter?

21.  Explain necessity of filter in the rectifier circuits.

22.  What are the advantages of a Π – type filter over the other filters.

23.  What are the limitations of voltage multiplying circuits?

24.  How are the voltage multiplier circuits classified?

25.  Why is a simple capacitor filter not suitable for heavy loads?

PART B

1.      Explain the Operation of  Half wave rectifier.

2.      Explain the Operation of  Full wave center tapped rectifier in detail.

3.      Explain the Operation of  Full wave Bridge rectifier in detail.

4.      Explain the Operation of  L-C filter with ripple factor calculation.

5.      Explain the Operation of  ∏ filters and calculate the ripple factor value.

6.      Differentiate L and C filter  and discuss the ripple factor values of L and c filter.

7.      What is a regulator? Explain its types

8.      Explain the Operation of SMPS.

9.      Explain the working of SCR used for Power control with suitable diagrams.

10.  Discuss in detail about the linear electronic voltage regulators.