VALLIAMMAI ENGINEERING COLLEGE SRM Nagar, Kattankulathur 603 203. DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING SUBJECT QUESTION BANK : EC6401 ELECTRONICS CIRCUITS-II SEM / YEAR: IV / II year B.E. UNIT I FEEDBACK AMPLIFIERS General Feedback Structure Properties of negative feedback Basic Feedback Topologies Feedback amplifiers Series Shunt, Series Series, Shunt Shunt and Shunt Series Feedback Determining the Loop Gain Stability Problem Nyquist Plot Effect of feedback on amplifier poles Frequency Compensation. Q. No Questions PART A BT Level Domain 1. Define positive and negative feedback. BTL 1 Remembering 2. List out the three networks that are connected around the basic BTL 1 Remembering amplifier to implement feedback concept. 3. Write about sensitivity and de-sensitivity of gain in feedback BTL 1 Remembering amplifiers. 4. Examine the gain with feedback for the amplifier with open loop BTL 1 Remembering gain of 300 and feedback factor of 0.1. 5. Tabulate the input and output resistances of a negative feedback BTL 1 Remembering amplifier. 6. Identify the type of feedback in the circuit. BTL 1 Remembering 7. Predict the loop gain or return ratio of feedback amplifier. BTL 2 Understanding
8. Discuss the advantages of negative feedback in amplifiers. BTL 2 Understanding 9. Give the reason for negative feedback which increases BTL 2 Understanding bandwidth. 10. Describe the effect of gain in amplifier when voltage shunt & BTL 2 Understanding series feedback is employed. 11. Discover the impact of negative feedback on noise and distortion BTL 3 Applying in amplifier circuits. 12. Calculate the percentage of negative feedback. If the voltage gain BTL 3 Applying of the amplifier is 150 and a feedback used to reduce the distortion of an amplifier by 80 %. 13. Illustrate the current series & current shunt feedback. BTL 3 Applying 14. Analyzing the feedback factor of an amplifier. BTL 4 Analyzing 15. Differentiate Phase margin and Gain margin. BTL 4 Analyzing 16. Explain the decrease in output impedance in feedback amplifiers. BTL 4 Analyzing 17. Summarize the effect of negative feedback on amplifier BTL 5 Evaluating characteristics. 18. Evaluating the Nyquist criterion for stability of feedback BTL 5 Evaluating amplifiers. 19. Creating the equivalent circuit of Trans-conductance amplifier. BTL 6 Creating 20. Compose the stability condition using Nyquist criterion. BTL 6 Creating PART B 1. Examine the expressions for gain with positive and negative BTL 1 Remembering feedback. [16] 2. List the effects of negative feedback on stability, distortion, noise, BTL 1 Remembering input and output impedance of a feedback amplifier. [16]
3. (i) A voltage-series negative feedback amplifier has a voltage gain without feedback as A = 500, input resistance R i = 3kΩ, output resistance R o = 20kΩ and feedback ratio β = 0.01. Identify the voltage gain A f, input resistance R if and output resistance R of of the amplifier with feedback. [8] (ii) The current-series feedback types of transistor amplifier for the given circuit diagram has the following parameters such as R 1 = 20kΩ, R 2 = 20kΩ, R L = 1KΩ, Re = 100Ω h fe = 80 and h ie = 2kΩ. Examine A, β, R if, A f, and the loop gain in db. [8] BTL 1 Remembering 4. Describe 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. [16] BTL 2 Understanding 5. Discuss the current shunt feedback connection and derive the BTL 2 Understanding expressions for R if and R of. [16] 6. An amplifier, without feedback, has a voltage gain of 500, lower cut-off frequency f 1 =100Hz,upper cut-off frequency f 2 = 250 khz and a distortion of 10%. Calculate the amplifier voltage gain, lower cut-off frequency and upper cut-off frequency and distortion, sensitivity, de-sensitivity and bandwidth when a BTL 3 Applying negative feedback is applied with feedback ratio of 0.01. [16] 7. (i) Illustrate the circuit diagram of voltage shunt feedback BTL 3 Applying amplifier [8] (ii)examine the expressions for R if and R of. [8] BTL 4 Analyzing
8. (i) An amplifier, with feedback has voltage gain of 100. If the gain without feedback changes by 20 % and the gain with feedback should not vary more than 2 %. If so, Analyzing the values of open loop gain A and feedback ratio β. [8] BTL 4 Analyzing (ii) For the given emitter follower circuit, Analyzing A i, R i, A v, R o & R of if R s = 600Ω, R L = 2kΩ, h fe = 80 and h ie = 5kΩ. [8] 9. Explain the current series feedback amplifier with neat block BTL 5 Evaluating diagram and derive the expressions for R if and R of. [16] 10. Design the structure of Nyquist criterion to Analyzing the stability BTL 6 Creating of feedback amplifiers. [16] UNIT II OSCILLATORS 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 collector oscillators, RC oscillators - phase shift Wienbridge - Twin-T Oscillators, Frequency range of RC and LC Oscillators, Quartz Crystal Construction, Electrical equivalent circuit of Crystal,Miller and Pierce Crystal oscillators, frequency stability of oscillators.. PART A Q.No Questions BT Level Domain 1. Define an oscillator. BTL 1 Remembering
2. Quote the Barkhausen criterion for an oscillator. BTL 1 Remembering 3. Tell the types of feedback oscillators. BTL 1 Remembering 4. List out the advantages of RC phase shift oscillator. BTL 1 Remembering 5. Label the equivalent circuit of an oscillator. BTL 1 Remembering 6. Write the advantages of crystal oscillator. BTL 1 Remembering 7. If L 1 = 1 mh, L 2 = 2 mh and C = 0.1 nf, Estimate the frequency BTL 2 Understanding of oscillation for Hartley oscillator. 8. Give the equivalent circuit of quartz crystal and mention its series BTL 2 Understanding and parallel resonant frequencies. 9. Express piezoelectric effect. BTL 2 Understanding 10. Illustrate the electrical equivalent circuit of Crystal oscillator. BTL 2 Understanding 11. A Wien bridge oscillator is used for operation at 10 khz. If the value of the resistor R is 100 KΩ, Calculate the value of Capacitor C. BTL 3 Applying 12. Classify the frequency range of RC and LC oscillators. BTL 3 Applying 13. Demonstrate the frequency stability of an oscillator. BTL 3 Applying 14. Order the types of RC & LC oscillators. BTL 4 Analyzing 15. Differentiate Hartley and Colpitts oscillator. BTL 4 Analyzing 16. Explain how the amplifier differs from oscillator. BTL 4 Analyzing 17. Judge how the feedback occurs in Armstrong Oscillator. BTL 5 Evaluating 18. In an RC phase shift oscillator, if R 1 = R 2 = R 3 = 200kΩ and C 1 = C 2 = C 3 = 100 pf. Evaluating the frequency of oscillations. BTL 5 Evaluating 19. Substitute L 2 = 0.4mH and C = 0.004F and the frequency of BTL 6 Creating oscillator F = 120kHz in the Hartley oscillator. Invent L 1 value by neglecting the mutual inductance. 20. Generalize the structure of an Oscillator. BTL 6 Creating PART B 1. List out the general condition for oscillation and derive the frequency of oscillation for a LC oscillator. [16] BTL 1 Remembering
2. Examine the working of a Hartley oscillator with a neat circuit diagram and derive the frequency of oscillation [16] BTL 1 Remembering 3. Describe the working of crystal oscillators with neat circuit BTL 1 Remembering diagrams. [16] 4. (i) In a transistorized Hartley oscillator, the two inductances are BTL 2 Understanding 2mH and 20µH while the frequency is to be changed from 950kHzto 2050kHz. Predict the range over which the capacitor is to be varied. [8] (ii) In a Hartley oscillator, the value of the capacitor in the tuned circuit is 500pF and the sections of the coil have inductances 38µH and 12µH. Express the frequency of oscillations and the feedback factor β. [8] 5. Discuss the working of Miller and Pierce crystal oscillators BTL 2 Understanding with neat circuit diagrams. [16] 6. Solve the expressions for frequency of oscillation and condition BTL 3 Creating for sustained oscillation of Colpiits oscillator with neat circuit diagram. [16] 7. (i) What is Wien Bridge oscillator? Calculate its BTL 3 Creating frequency of oscillation. [8] (ii) Explain the frequency stability of oscillator. [8] BTL 4 Analyzing 8. With neat circuit diagrams Analyzing the working principle of the following: [16] i. Tuned collector oscillator ii. Franklin oscillator BTL 4 Analyzing iii. Armstrong oscillator 9. Explain the working of Twin T oscillator with neat circuit BTL 5 Evaluating diagrams. Give any two applications [16]
10. Develop 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. [16] BTL 6 Creating UNIT III TUNED AMPLIFIERS Coil losses, 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 Stagger 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. PART A Q.No Questions BT Level Domain 1. Tell the advantages and disadvantages of tuned amplifier BTL 1 Remembering 2. Identify the ideal response and actual response of tuned BTL 1 Remembering amplifiers with diagram. 3. Define stagger tuned amplifier BTL 1 Remembering 4. Where does Q point is placed in a class C amplifier? BTL 1 Remembering 5. List the performance measure of tuned amplifier. BTL 1 Remembering 6. Outline gain product bandwidth of tuned amplifier. BTL 1 Remembering 7. Summarize the effect of cascading n stages of identical single BTL 2 Understanding tuned amplifiers on bandwidth 8. Estimate the bandwidth of a 3 stage cascaded single tuned BTL 2 Understanding amplifier if the resonant frequency is 455 KHz and the loaded Q of each stage is 10. 9. Express the need for neutralization. BTL 2 Understanding
10. Give the applications of class C tuned amplifier. BTL 2 Understanding 11. Illustrate the applications of tuned amplifiers. BTL 3 Applying 12. A tuned amplifier has its maximum gain at a frequency of 2 BTL 3 Applying MHz and has a bandwidth of 50 khz. Calculate the Q factor 13. Examine the efficiency of class C tuned amplifier. BTL 3 Applying 14. Differentiate loaded Q and unloaded Q. BTL 4 Analyzing 15. Compare single tuned and synchronously tuned amplifiers. BTL 4 Evaluating 16. Classify tuned amplifier BTL 4 Creating 17. Discriminate Hazeltine and modified Hazeltine neutralization. BTL 5 Evaluating 18. Deduce the magnitude of stagger tuned amplifier. BTL 5 Evaluating 19. An inductor of 250 µh has Q = 300 at 1MHz. Invent R s and R p BTL 6 Creating of the inductor. 20. Creating the equivalent circuit of neutralization BTL 6 Creating PART B 1. Examine the Q factor for inductor. [16] BTL 1 Remembering 2. (i)define class C tuned amplifier and derive its efficiency. [10] BTL 1 Remembering (ii)discuss about its frequency response [6] 3. Describe the principles involved in stagger tuned amplifier. [16] BTL 1 Remembering 4. 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 R t = 20 KΩ and output capacitance C o = 50 pf.estimate the values of inductance and capacitance of tuned circuit [16] BTL 2 Understanding 5. Discuss the effect of bandwidth on cascading single tuned BTL 2 Understanding amplifiers. [16] 6. (i)show the circuit diagram and equivalent circuit of a capacitor coupled single tuned amplifier and derive the expression for 3 db bandwidth. [10] (ii)sketch also the frequency response of the amplifier [6] BTL 3 Applying 7. (i) Illustrate the double tuned amplifier with neat circuit BTL 3 Applying
diagram and derive the expression for 3dB bandwidth. [10] (ii) Analyzing thefrequency response of the double tuned amplifier. [6] BTL 4 Analyzing 8. Explain the Small signal tuned amplifier with necessary BTL 4 Analyzing derivations. [16] 9. Evaluate the following with neat circuit diagram: BTL 5 Evaluating i. Hazeltine neutralization [10] ii. Neutrodyne neutralization [6] 10. Develop the circuit diagram of a two-stage synchronously tuned BTL 6 Creating amplifier and also its equivalent circuit. Derive the expression for bandwidth. [16] UNIT IV WAVE SHAPING AND MULTIVIBRATOR CIRCUITS RC & RL Integrator and Differentiator circuits Storage, Delay and Calculation of Transistor Switching Times Speed-up Capacitor - Diode clippers, Diode comparator - Clampers. Collector coupled and Emitter coupled Astable multivibrator Monostable multivibrator - Bistablemultivibrators Triggering methods for Bistablemultivibrators - Schmitt trigger circuit PART A Q.No Questions BT Level Domain 1. When can diode act as a comparator? BTL 1 Remembering 2. Define clipper BTL 1 Remembering 3. Describe a simple clamper circuit. BTL 1 Remembering 4. Outline rise time and storage time. BTL 1 Remembering 5. Mention the applications of bistable multivibrator BTL 1 Remembering 6. List the types of multivibrators. BTL 1 Remembering 7. In a low pass RC circuit, rise time is 35 ns. Estimate the BTL 2 Understanding bandwidth that can be obtained using the circuit. 8. Summarize the disadvantages of using diode as a shunt BTL 2 Understanding element in clipper circuit 9. Give the applications of clippers and clampers. BTL 2 Understanding 10. Differentiate symmetrical triggering and unsymmetrical BTL 2 Understanding
triggering. 11. Illustrate the role of commutating capacitor and draw its BTL 3 Applying circuit. 12. Calculate the value of capacitors to be used in an astable BTL 3 Applying multivibrator to provide a train of pulse 2 µsec wide at a repetition rate of 75 khz with R 1 =R 2 =10 KΩ. 13. Specify the applications of Schmitt trigger circuit. BTL 3 Applying 14. Explain how the high pass RC circuit acts as a differentiator. BTL 4 Analyzing 15. Compare Astable, Monostable and Bistable multivibrators. BTL 4 Analyzing 16. Classify the types of multivibrator. BTL 4 Analyzing 17. List any two applications of astable multivibrator. BTL 5 Evaluating 18. Measure the duration of Astable &Monostable multivibrator BTL 5 Evaluating output. 19. Design the circuit of RC integrator and mention the condition BTL 6 Creating under which the circuit behaves as an integrator. 20. Develop a clipper circuit which clips all voltages above +2 V. BTL 6 Creating PART B 1. (i)with neat circuit diagram and waveforms, describe the BTL 1 Remembering operation of collector coupled astable multivibrator which uses transistors. [10] (ii)derive the expression for pulse width of collector of collector coupled astable multivibrator(6) 2. Describe the working principle of Bistable multivibrator with neat diagrams. [16] BTL 1 Remembering 3. Identify the different types of triggering used for bistable BTL 1 Remembering multivibrator. [16] 4. Summarize the response of low pass RC circuit to the following BTL 2 Understanding input waveforms: (i). Step (4) (ii) Pulse(4) (iii) Square(4) (iv)ramp(4) 5. Discuss the transistor switching circuit and its response for a pulse input. [8] Explain the following terms for this circuit: [8] i. Delay time BTL 2 Understanding
ii. Turn on time
iii. Storage time iv. Fall time and v. Turn-off time 6. Examine the operation of positive and negative diode clippers with waveforms [16] BTL 3 Applying 7. (i) Illustrate how Schmitt trigger circuit can be evolved from a BTL 3 Applying bistable circuit. [8] (ii) Explain the working principle of Monostable multivibrator with neat diagrams [8] BTL 4 Analyzing 8. Analyze the expression for UTP and LTP in Schmitt trigger BTL 4 Analyzing with circuit diagrams. [16] 9. Briefly discuss about the one shot multivibrator with neat BTL 5 Evaluating circuit diagrams and waveforms. [10] Deduce the expression and mention its advantages and disadvantages. [6] 10. Design a Schmitt trigger circuit for the data given: V cc = 20, BTL 6 Creating UTP = 5V and LTP= 3 V. I c sat = 2 ma and h fe (min) = 100. Draw the designed circuit. [16] UNIT V BLOCKING OSCILLATORS & TIME BASE GENERATORS UJT saw tooth waveform generator, Pulse transformers equivalent circuit response - applications,blocking Oscillator Free running blocking oscillator - Astable Blocking Oscillators with base timing Push-pull Astable blocking oscillator with emitter timing, Frequency control using core saturation,triggered blocking oscillator Monostable blocking oscillator with base timing Monostable blockingoscillator with emitter timing, Time base circuits - Voltage-Time base circuit, Current-Time base circuit Linearization through adjustment of driving waveform. PART A Q.No Questions BT Domain Level 1. When oscillator does is called as a free running blocking BTL 1 Remembering oscillator? 2. List the advantage of core saturation method of frequency BTL 1 Remembering
control in a blocking oscillator. 3. List any two methods of achieving sweep linearity of a time- BTL 1 Remembering base waveform. 4. Define duty cycle. BTL 1 Remembering 5. Write about Sweep time. BTL 1 Remembering 6. Describe the operation of UJT BTL 1 Remembering 7. Give the applications of blocking oscillator. BTL 2 Understanding 8. Differentiate restoration time and sweep time of a time- BTL 2 Understanding base signal. 9. Express the equivalent circuit of pulse transformer. Mention BTL 2 Understanding the various elements. 10. Summarize applications of the pulse transformer. BTL 2 Understanding 11. Show the equivalent circuit of a pulse transformer and state BTL 3 Applying its applications. 12. Compute the equation used to determine sweep frequency of BTL 3 Applying a UJT relaxation oscillator. Calculate the frequency with R = 100 KΩ, C = 0.4 µf and intrinsic stand-off ratio 0.57. 13. Illustrate the slope error of a voltage sweep waveform. BTL 3 Applying 14. Classify the voltage and current time base generators. BTL 4 Analyzing 15. Compare sweep speed error and transmission error. BTL 4 Analyzing 16. Analyze the restoration time or flyback time BTL 4 Analyzing 17. Judge the function of time base circuit. BTL 5 Evaluating 18. Assess the applications of blocking oscillator. BTL 5 Evaluating 19. Design a complete equivalent circuit of pulse transformer. BTL 6 Creating 20. Develop the equivalent circuit of UJT. BTL 6 Creating PART B 1. Describe the operation of a RC controlled astable transistor BTL 1 Remembering blocking oscillator with circuit diagram and waveforms. [16]
2. Examine the operation of a triggered blocking oscillator with emitter timing. [8] Sketch the circuit and waveforms and also derive the expression for t p of emitter timing blocking oscillator. [8] 3. (i)identify how the push-pull Astable blocking oscillator works. [8] (ii)give necessary neat circuit diagram and explain. [8] BTL 1 BTL 1 Remembering Remembering 4. (i)discuss how an Astable circuit acts as a free running blocking BTL 2 Understanding oscillator.[8] (ii) Draw the free running blocking oscillator circuit and explain the operation. [8] 5. Summarize Miller integrator and current time-base circuit BTL 2 Understanding waveforms. [16] 6. The diode controlled Astable blocking oscillator has the parameters V c = 10 V, V b = 5 V, C 1 = C 2 = 2 nf, V r = 9V, L = 3 mh and C = 100 pf. Calculate the frequency of oscillation and duty cycle. [16] 7. (i) Illustrate the working of saw tooth generator using UJT with suitable circuit and waveforms [8] (ii) Analyze the expression for the oscillating frequency of UJT. [8] 8. Compare RC controlled and Diode controlled Astable blocking oscillator. [16] 9. Consider a UJT sweep circuit, the resistance is 20 KΩ while the capacitance is 0.2 µf. The valley potential is 1.5 V when V BB = 15 V. Assuming diode cut in voltage of 0.7 V and intrinsic stand-off ratio as 0.5, Evaluating the frequency of oscillations. [16] BTL 3 BTL 3 BTL 4 BTL 4 BTL 5 Applying Applying Analyzing Analyzing Evaluating 10. (i)design the circuit of Bootstrap voltage time base generator [8] BTL 6 Creating (ii)explain the quiescent conditions, formation of sweep, retrace interval and recovery process. [8]