BHARATHIDASAN ENGINEERING COLLEGE

BHARATHIDASAN ENGINEERING COLLEGE DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING EC6401 - ELECTRONIC CIRCUITS - II QUESTION BANK II- YEAR IV SEM ACDEMIC YEAR: 2016-2017 EVEN SEMESTER

EC6401 ELECTRONIC CIRCUITS II L T P C 3 0 0 3 UNIT I FEEDBACK AMPLIFIERS 9 General Feedback Structure Properties of negative feedback Basic Feedback Topologies Feedbackamplifiers Series Shunt, Series Series, Shunt Shunt and Shunt Series Feedback Determining the Lop Gain Stability Problem Nyquist Plot Effect of feedback on amplifier poles Frequency Compensation. UNIT II OSCILLATORS 9 Classification, Barkhausen Criterion - Mechanism for start of oscillation and stabilization of amplitude, General form of an Oscillator, Analysis of LC oscillators - Hartley, Colpitts, Clapp, Franklin, Armstrong, Tuned collectoroscillators, RC oscillators - phase shift Wien bridge - Twin-T Oscillators, Frequency range of RC and LC Oscillators, Quartz Crystal Construction, Electrical equivalent circuit of Crystal, Miler and Pierce Crystal oscillators, frequency stability of oscillators. UNIT III TUNED AMPLIFIERS 9 Coil loses, unloaded and loaded Q of tank circuits, small signal tuned amplifiers - Analysis of capacitor coupled single tuned amplifier double tuned amplifier - effect of cascading single tuned and double tuned amplifiers on bandwidth Stager tuned amplifiers large signal tuned amplifiers Class C tuned amplifier Efficiency and applications of Class C tuned amplifier - Stability of tuned amplifiers Neutralization - Hazeltine neutralization method. UNIT IV WAVE SHAPING AND MULTIVIBRATOR CIRCUITS 9 RC & RL Integrator and Differentiator circuits Storage, Delay and Calculation of Transistor Switching Times Sped-up Capacitor - Diode clippers, Diode comparator - Clampers. Collector coupled and Emitter coupled Astablemultivibrator Monostablemultivibrator - Bistable multivibrators Triggering methods for Bitable multivibrators - Schmitttrigger circuit UNIT V BLOCKING OSCILLATORS AND TIMEBASE GENERATORS 9 UJT sawtooth waveform generator, Pulse transformers equivalent circuit response - applications,blocking Oscillator Freerunning blocking oscillator - Astable Blocking Oscillators with base timing PushpullAstable blocking oscillator with emitter timing, Frequency control using core saturation,triggered blocking oscillator Monostable blocking oscillator with base timing Monostable blocking oscillator with emitter timing, Time base circuits - Voltage-Time base circuit, Current-Time base circuit Linearization through adjustment of driving waveform. TOTAL: 45 PERIODS TEXT BOOK: Sedra and Smith, Micro Electronic Circuits ; Sixth Edition, Oxford University Press, 2011. REFERENCES: Robert L. Boylestad and Louis Nasheresky, Electronic Devices and Circuit Theory, 10th Edition, Pearson Education /PHI, 2008 David A. Bel, Electronic Devices and Circuits, Fifth Edition, Oxford University Press, 2008. Milman J. and Taub H., Pulse Digital and Switching Waveforms, TMH, 2000. Milman and Halkias. C., Integrated Electronics, TMH, 2007.

UNIT I (FEEDBACK AMPLIFIERS) PART A 1. Define positive and negative feedback. ( May/June 2012) 2. What is the impact of negative feedback on noise in circuits? (Apr/May 2010) 3. Mention the three networks that are connected around the basic amplifier to implement feedback concept. (Apr/May 2011) 4. What is loop gain or return ratio? (Apr/May 2011) 5. Define feedback factor of a feedback amplifier. ( May/June 2012) 6. What are the advantages of negative feedback in amplifiers? (Apr/May 2015) 7. Justify that negative feedback increases bandwidth.(nov /Dec 2010) 8. Define sensitivity and de-sensitivity of gain in feedback amplifiers. (Apr/May 2010) 9. What is the impact of negative feedback on noise and distortion in amplifier circuits? (Apr/May 2010) 10. State the effect on output resistance and input resistance of amplifier when voltage shunt feedback is employed. ( May/June 2012) 11. Determine the gain with feedback for the amplifier with open loop gain of 300 and feedback factor of 0.1. (May/June 2013) 12. Draw the equivalent circuit of Transconductance amplifier. ( May/June 2014) 13. What are the steps to be carried out for complete analysis of a feedback amplifier? 14. A negative feedback is used to reduce the distortion from an amplifier by 80 %. What must be the percentage negative feedback to accomplish this if the amplifier voltage gain is 150? 15. What happens to the input and output resistances of a negative feedback amplifier? 16. Identify the type of feedback in the circuit

16. State the Nyquist criterion for stability of feedback amplifiers. (Apr/May 2015) 17. What is Nyquist diagram? ( May/June 2014) 18. Define phase margin and gain margin. 19. Define CMRR and write its significance in differential amplifiers. 20. Mention the operating modes of Differential amplifier. 21. List out the characteristics of an amplifier which are modified by negative feedback. (Nov/Dec 2013) 22. Draw the schematic diagram of a free running blocking oscillator.(apr/may 2015) 23. State Barkhausen Criterion.(Apr/May 2015) 24. Draw the magnitude and phase angle plot of three stage amplifier.(nov/dec 2015) 25. In a Negative feedback amplifier A=100, β=0.04 Vs=50mV, Find a) gain with feedback (b) output voltage (c) feedback factor. (Nov/Dec 2013) PART B 1. Derive the expressions for gain with positive and negative feedback. (Apr/May 2011) 2. What is the effect of negative feedback on stability, distortion, noise, input and output impedance of a feedback amplifier? (Apr/May 2015) 3. An amplifier, without feedback, has a voltage gain of 500, lower cut-off frequency f1 = 100 Hz, upper cut-off frequency f2 = 250 KHz and a distortion of 10%. Determine the amplifier voltage gain, lower cut-off frequency and upper cut-off frequency and distortion, when a negative feedback is applied with feedback ratio of 0.01. (Apr/May 2011) 4. An amplifier, 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 β. (Apr/May 2011) 5. What is the effect of a voltage series feedback on input and output resistance of a BJT amplifier? Explain the same, with necessary circuit, equivalent circuit and equations. (May/June 2012) 6. Draw the circuit diagram of voltage shunt feedback amplifier and derive the expressions for Rif and Rof. (May/June 2014) 7. With block diagram of current series feedback and derive the expressions for Rif and Rof. (Nov/Dec 2010)

8. Explain the current shunt feedback connection and derive the expressions for Rif and Rof. (Apr/May 2013) 9. Transistors in the feedback amplifier shown in figure are identical and the parameters are hie = 1.1 K, hfe = 50, hre = hoe = 0. Identify the feedback amplifier and calculate Aof, Rif and Rof. (Nov/Dec 2010) 10. Explain Nyquist criterion to analyse the stability of feedback amplifiers.

1. Define oscillator. (Nov/Dec 2013) UNIT II (OSCILLATORS) PART A 2. State the Barkhausen criterion for an oscillator. ( May/June 2014) 3. Give the types of oscillators. 4. Draw & Explain theelectrical equivalent circuit of Quartz Crystal. (May/June 2014) 5. Mention two essential conditions for a circuit to maintain oscillations. (Apr/May 2010) 6. State the advantages of clapp oscillator. (Nov/Dec 2004) 7. Why a LC tank circuit does not produce sustained oscillations? How can this be overcome? (Nov/Dec 2011) 8. What is the major disadvantage of Twin T oscillator? (Nov/Dec 2014) 9. Mention the expression for frequency of oscillation for Hartley and Colpitts oscillator. 10. If L1 = 1 mh, L2 = 2 mh and C = 0.1 nf, what is the frequency of oscillation of the Hartley oscillator? (Nov/Dec 2015) 11. A wien bridge oscillator is used for operation at 10 KHz. If the value of the resistor R is 100 K, what is the value of C required? (Apr/May 2011) 12. What are the advantages and disadvantages of RC phase shift oscillator? (May/June 2016) 13. Give the equivalent circuit of quartz crystal and mention its series and parallel resonant frequencies. 14. In a RC phase shift oscillator if its frequency of oscillation os 955Hz & R1=R2=R3=680KΩ.Find the value of capacitors.(nov/dec 2010) 15. What are the features of crystal oscillator? 13. Mention the frequency range of RC and LC oscillators. (Apr/May 2015) 14. What is frequency stability of an oscillator? (Apr/May 2010) 15. A crystal has the following parameters L = 0.3 H, C = 0.06 pf, and mounting capacitance is 3 pf. Calculate its series and parallel resonant frequencies.

16. State piezoelectric effect.(apr/may 2011) 17. List the advantages of crystal oscillator. 18. How does the amplifier differ from oscillator? 19. Draw the equivalent circuit of Crystal oscillator. (Apr/May 2015) 20. State Miller theorem. PART B 1. Derive the general condition for oscillation for a LC oscillator and derive the frequency of oscillation for a colpitts oscillator. (Nov/Dec 2010) 2. Explain the working of a Hartley oscillator with a neat circuit diagram and derive the frequency of oscillation. (Nov/Dec 2012) 3. Derive the expressions for frequency of oscillation and condition for sustained oscillation of Hartley oscillator with neat circuit diagram. 4. A Hartley oscillator has L1 = 5 mh, L2= 25 mh and frequency of oscillation ranging from 700 KHz to 1 MHz. Determine the value of Cover this frequency range. 5. With neat circuit diagrams explain the working principle of the following? (Apr/May 2012) i. Tuned collector oscillator ii. Franklin oscillator iii. Armstrong oscillator 6. What is a Wien Bridge? How is it used as an oscillator? Derive the necessary equations.(nov/dec 2012) 7. Draw the circuit diagram and explain the working principle of RC phase shift oscillator. Also derive the expression for frequency of oscillation and condition for sustained oscillation.(apr/may 2014) 8. Explain the working of Miller and Pierce crystal oscillators with neat circuit diagrams. Give two applications. (Nov/Dec 2011) 9. Explain the working of Clap oscillator with neat circuit diagrams. Give two applications. (Nov/Dec 2014)

UNIT III (TUNED AMPLIFIERS) PART A 1. What is a tuned amplifier? Mention its advantages and disadvantages. (Apr/May 2010) 2. Draw the ideal response and actual response of tuned amplifiers. 3. Define loaded Q and unloaded Q. (Nov/Dec 2010) 4. An inductor of 250 µh has Q = 300 at 1MHz. Determine Rs and Rp of the inductor. 5. Mention any two applications of tuned amplifiers. 6. Mention the important features of stagger tuned amplifier. (May/June 2013) 7. A tuned amplifier has its maximum gain at a frequency of 2 MHz and has a bandwidth of 50 KHz. Calculate the Q factor.(nov/dec 2011) 8. What is the effect of cascading n stages of identical single tuned amplifiers on bandwidth? (Nov/Dec 2008) 9. Determine the bandwidth of a 3 stage cascaded single tuned amplifier if the resonant frequency is 455 KHz and the loaded Q of each stage is 10. (Apr/May 2004) 10. A tuned circuit has a resonant frequency of 1600KHz & bandwidth of 10 KHz. What is the value of its Q-factor? (Apr/May 2012) 11. What is class C tuned amplifier? Mention its efficiency. 12. Where the Q point is placed in a class C amplifier? (Apr/May 2008) 13. Differentiate single tuned and synchronously tuned amplifiers. (Nov/Dec 2007) 14. What is the need for neutralization? (Apr/May 2014) 15. What is narrow band neutralization? (Apr/May 2012) 16. Draw the circuit of Hazeltine neutralization. (Apr/May 2009) 17. Classify tuned amplifier 18. Mention the applications of class c tuned amplifier.(may/june 2013)

19. What is stagger tuned amplifier. (Nov/Dec 2011) 20. List the performance measure of tuned amplifier. 21. Define gain product bandwidth of tuned amplifier. 1. Derive the Q factor for inductor. PART B 2. Draw the circuit diagram and equivalent circuit of a capacitor coupled single tuned amplifier and derive the expression for 3 db bandwidth. Sketch also the frequency response of the amplifier. (Nov/Dec 2013) 3. With neat circuit diagram explain double tuned amplifier and derive the expression for 3 db bandwidth. Sketch also the frequency response of the amplifier. (Nov/Dec 2012) 4. Draw the circuit diagram of a two-stage synchronously tuned amplifier and also its equivalent circuit. Derive the expression for bandwidth. (Apr/May 2013) 5. A single tuned transistor amplifier is used to amplify modulated RF carrier of 600 KHz and a bandwidth of 15 KHz. The circuit has total output resistance Rt = 20 K and output capacitance Co = 50 pf. Calculate the values of inductance and capacitance of tuned circuit. (Apr/May 2012) 6. Discuss the effect of bandwidth on cascading single tuned amplifiers. (Nov/Dec 2013) 7. Explain class C tuned amplifier and derive its efficiency. Also discuss about its frequency response. (Apr/May 2014) 8. Explain the following with neat circuit diagram: (Apr/May 2011) i. Hazeltine neutralization ii. Neutrodyne neutralization 9. Explain the Small signal tuned amplifier with necessary derivations. (Apr/May 2014) 10. Describe the principles involved in stagger tuned amplifier. (Nov/Dec 2013)

UNIT IV (WAVE SHAPING AND MULTIVIBRATOR CIRCUITS) PART A 1. How does diode act as a comparator? (Nov/Dec 2010) 2. Draw the circuit of RC integrator and mention the condition under which the circuit behaves as an integrator. (Nov/Dec 2008) 3. Explain how the high pass RC circuit acts as a differentiator? 4. In a low pass RC circuit, rise time is 35 nano seconds. What is the bandwidth that can be obtained using the circuit? (Nov/Dec 2012) 5. What are the disadvantages of using diode as a shunt element in clipper circuit? 6. What is a clipper? (Apr/May 2011) 7. Draw a clipper circuit which clips all voltages above +2 V. 8. Describe a simple clamper circuit. (Apr/May 2012) 9. State the applications of clippers and clampers. 10. What is the role of commutating capacitor? Draw the circuit. (Apr/May 2015) 11. Define rise time and storage time. (Nov/Dec 2007) 12. Why do we call astable multivibrator as free running multivibrator? (Nov/Dec 2006) 13. State any two applications of astable multivibrator. (Apr/May 2016) 14. Determine the value of capacitors to be used in an astable multivibrator to provide a train of pulse 2 µsec wide at a repetition rate of 75 KHz with R1=R2=10 K. (Nov/Dec 2013) 15. Differentiate symmetrical triggering and unsymmetrical triggering.(nov/dec 2011) 16. Why is monostable multivibrator also called as delay circuit? (Nov/Dec 2009) 17. What are the advantages and disadvantages of bistable multivibrator? 18. Mention the applications of bistable multivibrator. (Apr/May 2011) 19. State the applications of Schmitt trigger circuit. (May/June 2012) 20. Draw the Clipper Circuits for two independent clipping levels. (Apr/May 2015) 21. What is a regenerative comparator? Give an example circuit. (May/June 2013) 22. List the types of multivibrators.

PART B 1. Derive and draw the response of low pass RC circuit to the following input waveforms: (Apr/May 2012) a. Step b. Pulse c. Square 2. Explain the operation of positive and negative diode clippers with waveforms. (Apr/May 2011) 3. Draw a transistor switching circuit and its response waveform for a pulse input. For such a circuit, explain the following terms: (May/June 2014) i. Delay time ii. Turn on time iii. Storage time iv. Fall time and v. Turn-off time 4. With neat circuit diagram and waveforms, explain the operation of collector coupled astable multivibrator which uses transistors. Derive the expression for pulse width. (Apr/May 2014) 5. Briefly discuss about the one shot multivibrator with neat circuit diagrams and waveforms. Derive the expression and mention its advantages and disadvantages. (Apr/May 2011) 6. Explain the working principle of Bistable multivibrator with neat diagrams and illustrate how Schmitt trigger circuit can be evolved from a bistable circuit? (Nov/Dec 2011) 7. Explain the different types of triggering used for bistable multivibrator. (Nov/Dec 2007) 8. With circuit diagrams explain Schmitt trigger operation. Obtain the expression for UTP and LTP. (Apr/May 2008) 9. Design a Schmitt trigger circuit for the data given: Vcc = 20, UTP = 5V and LTP= 3 V. Ic sat = 2 ma and hfe (min) = 100. Draw the designed circuit. (Apr/May 2011) 10. Explain the working principle of Monostable multivibrator with neat diagrams. (Nov/Dec 2008) 11. Discuss on the effect of RC time constant & condition for the circuit to operate as integrator. (Apr/May 2015) 12. Determine the value of capacitors to be used in an astable multivibrator to provide a train of pulse, 2µ wide, at a repetition rate of 100KHz,if R1=R2=20KΩ. (May/June 2012)

UNIT V (BLOCKING OSCILLATORS & TIME BASE GENERATORS) PART A 1. What are the applications of blocking oscillator? (Apr/May 2013) 2. Mention the applications of pulse transformers. (Apr/May 2015) 3. Draw the equivalent circuit of a pulse transformer and state its applications. (May/June 2014) 4. Draw the circuit diagram of a free running blocking oscillator. (Apr/May 2015) 5. What is the advantage of core saturation method of frequency control in a blocking oscillator? 6. Write the equation used to determine sweep frequency of a UJT relaxation oscillator. Calculate the frequency with R = 100 K, C = 0.4 µf and intrinsic stand-off ratio 0.57. (Nov/Dec 2014) 7. State any two methods of achieving sweep linearity of a time-base waveform. 8. What is restoration time and sweep time of a time-base signal? (May/June 2012) 9. What is the function of time base circuit? (Apr/May 2011) 10. Draw a transistorized bootstrap time base generator circuit. (Nov/Dec 2010) 11. Define Slope error & Displacement error. (May/June 2013) 10. Define duty cycle. 11. What do you meant by voltage and current time base generators? 12. Define sweep speed error and transmission error. 13. Sketch and define the slope error of a voltage sweep waveform. (Apr/May 2011) 14. What is pulse transformer? (Nov/Dec 2006) 15. Draw the equivalent circuit of pulse transformer. Explain the various elements in it.? (Nov/Dec 2006) 16. Mention the application of the pulse transformer. (Nov/Dec 2009) 17. Define the displacement error of a sweep voltage 18. Define restoration time or fly back time 19. Define Sweep time. 20. What is UJT?

PART B 1. With circuit diagram and waveforms, explain the operation of a RC controlled astable transistor blocking oscillator. (May/June 2014) 2. 3. Explain about astable blocking oscillator with base timing. (Apr/May 2010) 4. Design a Schmitt trigger using BJT with UTP=5V & LTP=2V. Assume Vcc=15 V Ic 2=5mA & hfe=100.(apr/may 2015) 5. How does an Astable circuit acts as a free running blocking oscillator? Draw the circuit and explain. (Nov/Dec 2011) 6. Compare RC controlled and Diode controlled Astable blocking oscillator. (Apr/May 2008) 7. Describe the operation of a triggered blocking oscillator with emitter timing. Sketch the circuit and waveforms and also derive the expression for tp. 8. The diode controlled Astable blocking oscillator has the parameters Vc = 10 V, Vb= 5 V, C1 = C2 = 2 nf, Vr = 9V, L = 3 mh and C = 100 pf. Calculate the frequency of oscillation and duty cycle.. (Apr/May 2010) 9. With suitable circuit and waveforms, explain the working of UJT saw tooth generator. Derive the expression for the oscillating frequency. (May/June 2013) 10. For a certain UJT sweep circuit, the resistance is 20 K while the capacitance is 0.2 µf. The valley potential is 1.5 V when VBB = 15 V. Assuming diode cut in voltage of 0.7 V and intrinsic stand-off ratio as 0.5, calculate the frequency of oscillations. (Apr/May 2006) 11. Draw the circuit of Bootstrap voltage time base generator and explain the quiescent conditions, formation of sweep, retrace interval and recovery process. (Nov/Dec 201100) 12. Write about Miller integrator and current time-base circuit waveforms. (Apr/May 2010) 10. How does a push-pull Astable blocking oscillator working? Draw the circuit and explain. (May/June 2014)