SIDDHARTH GROUP OF INSTITUTIONS :: PUTTUR (AUTONOMOUS) Siddharth Nagar, Narayanavanam Road 517583 QUESTION BANK Subject with Code : Electronic Circuit Analysis (16EC407) Year & Sem: II-B.Tech & II-Sem Course & Branch: B.Tech - ECE Regulation: R16 UNIT I SMALL SIGNAL LOW FREQUENCY TRANSISTOR AMPLIFIER ANALYSIS 1. a) Draw the h-parameter equivalent circuit for CE configuration and determine the expression for h-parameters. [L3][CO1][10M] b) List the benefits of h-parameters. [L2][CO1][2M] 2. Derive the equations for voltage gain, current gain, input impedance and output admittance for a BJT using low frequency h-parameter model for CE configuration. [L4][CO1][12M] 3. Consider a single stage CE amplifier with R s = 1kΩ, R 1 = 50kΩ, R 2 = 2kΩ, R c = 1kΩ, R L = 1.2kΩ, h fe =50, h ie =1.1k, h oe = 25µA/V and h re = 2.5 x 10-4, as shown in Fig. Find A I, R i, A v, A vs, A IS and R 0. [L5][CO1][12M] 4. a) With neat diagram, explain the simplified hybrid model for CE configuration. [L2][CO1][6M] b) Derive the parameters current gain, voltage gain, input impedance and output impedance of CB configuration using simplified hybrid model. [L4][CO1][6M] 5. a) Determine the parameters A I, R i, A v and R 0 of Common Collector configuration using approximate analysis. [L3][CO1][6M] Electronic Circuit Analysis Page 1
b) A voltage source of internal resistance R s = 900Ω drives a CC amplifier using load resistance R L =2000Ω. The CE h parameters are h fe =60, h ie =1.2k, h oe = 25µA/V and h re = 2 x 10-4. Compute A I, R i, A v and R 0 using approximate analysis. 6. A CE amplifier is driven by a voltage source of internal resistance R s = 800Ω and the load impedance of R L =1000Ω. The h-parameters are h ie =1k, h fe =50, h oe = 25µA/V and h re = 2 x 10-4. Calculate current gain, voltage gain, input impedance and output impedance using exact analysis and also using approximate analysis. [L5][CO1][12M] 7. a) Explain the analysis and design of single stage RC coupled Amplifier. [L2][CO1][6M] b) Compare the transistor amplifier parameters for CE, CB and CC configurations. [L4][C01][6M] 8. a) Obtain the expression for current gain, voltage gain, input impedance and output impedance for Common Emitter Amplifier with Emitter Resistor. [L4][CO1][6M] b) A CE amplifier is driven by a voltage source of internal resistance R s = 1000Ω and the load impedance of R C =2kΩ. The h-parameters are h ie =1.3k, h fe =55, h oe = 22µA/V and h re = 2 x 10-4. Neglecting biasing resistors, compute current gain, voltage gain, input impedance, output impedance and output terminal resistance R 0T for the value of Emitter Resistor R E = 200Ω inserted in the emitter circuit. 9. a) Derive input impedance, output impedance and voltage gain of JFET Common Source Amplifier with fixed bias. [L4][CO1][6M] b) For the circuit shown in Fig. determine input impedance, output impedance and voltage gain. [L3][CO1][6M] 10. a) Derive input impedance, output impedance and voltage gain of JFET Common Source amplifier with voltage divider bias for bypassed R s. [L4][CO1][6M] b) For the circuit shown in Fig. determine input impedance, voltage gain, output impedance Z 0 and Z 0. Assume for FET g m = 2mA/V, r d = 10kΩ. [L3][CO1][6M] Electronic Circuit Analysis Page 2
11. Derive input impedance, output impedance and voltage gain of JFET Common Drain Amplifier with neat diagram. [L4][CO1][12M] UNIT II SMALL SIGNAL HIGH FREQUENCY TRANSISTOR AMPLIFIER ANALYSIS 1. a) Draw the Hybrid- π model of a Transistor and explain the significance of each elements in the model. [L2][CO1][6M] b) Explain the significance of Hybrid π capacitances and derive the expression for C de. [L2][CO1][6M] 2. Derive the expression for the hybrid π parameters g m, g b e, g b c, r bb and g ce. [L4][CO1][12M] 3. a) Explain the dependence of hybrid parameters upon collector c urrent, V CE and Temperature. [L2][CO1][6M] b) A BJT has the following parameters measured at I c =1mA, h ie =3kΩ, h fe =100, C c =2pF and C e =18pF. Find r b e, r bb, and g m for R L =1KΩ. 4. a) Give the typical values of Hybrid- π parameters. [L2][CO1][6M] b) A BJT has h ie =6kΩ and h fe =224 at I C = 1mA, with f T =80MHz and C b c =12pF. Determine g m, r b e, r bb and c b e of the small signal high frequency model of BJT at room temperature and collector current of 1mA. 5. Derive the expression for CE Short circuit current gain with the help of necessary circuit diagrams and approximations. [L5][CO1][12M] 6. Derive the expression for Current gain with R L and explain the variation of frequency response with R L. [L5][CO1][12M] 7. a) Derive the expression for cut off frequencies f α, f β and f T. b) Short circuit CE current gain of a transistor is 25 at a frequency of 2MHz. If f β = 200KHz Calculate (i) f T (ii) h fe (iii) Find A i at frequency of 10MHz and 100MHz. 8. Derive the expression for gain bandwidth product for voltage and current. [L4][CO1][12M] Electronic Circuit Analysis Page 3
9. a) At I c = 1mA and V CE =10V, a certain transistor data shows C c = C b c = 3pF, h fe = 200 and w T = - 500 M rad/sec. Calculate g m, r b e, C e = C b e and w β. [L5][CO1][10M] b) Define Unity Gain Frequency f T. [L1][CO1][2M] 10. a) A high frequency amplifier uses a transistor which is driven from a source with R s = 0. Calculate value of f H, if R L = 1kΩ. Assume typical values of hybrid π parameters. b) For a BJT amplifier, the following values are known: operating temperature T = 300 0 K. I CQ = 2mA, r bb = 100Ω, r b e = 2MΩ, r ce = 80kΩ, C b e = 200pF, C b c = 3pF, f T = 50MHz. Obtain the h parameters if k=1.381 x 10-23 j/ 0 K and q = 1.6 x 10-19 C. UNIT III MULTISTAGE AMPLIFIERS 1. (a) Explain the classification of amplifiers. (b) Discuss the need of cascading amplifiers. 2. Describe different methods used for coupling multistage amplifiers with their frequency response. [L1][CO2][12M] 3. Draw the block diagram of n-stage cascaded amplifier and analyze its various parameters. [L4][CO2][12M] 4. With neat diagram, analyze the two stage RC coupled amplifier. [L4][CO2][12M] 5. The following figure shows CE-CE cascade amplifier with their biasing arrangements. Calculate R i, A i, A v, R i, A vs and A is if circuit parameters are: R s =1K, R c1 = 15K, R E1 = 100Ω, R C2 = 4 KΩ, R E2 = 330Ω with R 1 = 200K and R 2 = 20K for first stage and R 1 = 47K and R 2 = 4.7K for second stage. Assume that h ie = 1.2kΩ, h fe = 50, h re = 2.5 x 10-4 and h oe = 25 x 10-6 A/V. [L5][CO2][12M] 6. With neat diagram explain cascode amplifier and derive the parameters of cascode amplifier. [L2][CO2][12M] 7. What is Darlington Connection? With diagram, derive the parameters of Darlington Electronic Circuit Analysis Page 4
amplifier. [L4][CO2][12M] 8. Explain how the input impedance is increased by Bootstrap Emitter Follower with neat diagram. [L2][CO2][12M] 9. For the circuit shown in Fig. Calculate R i, A i, A V and R o. h ie =1.1k, h fe =50, h oe = 25µA/V and h re = 2.5 x 10-4. [L5][CO2][12M] 10. a) Explain the effect of cascading of amplifiers on bandwidth. b) An amplifier consists of 3 identical stages in cascade, the bandwidth of overall amplifier extends from 20 Hz to 20 khz. Calculate the bandwidth of individual stage. [L5][C02][6M] UNIT IV FEEDBACK AMPLIFIERS AND OSCILLATORS 1. Explain the characteristics of negative feedback amplifiers. [L2][CO2][12M] 2. a) Explain Feedback topologies. b) An amplifier has an open loop gain of 1000 and a feedback ratio of 0.04. If the open loop gain changes by 10% due to temperature, find the percentage change in gain of the amplifier with feedback. [L3][CO2][6M] 3. a) Derive the expressions of input and output resistances for Voltage Series FBA. [L4][CO2][6M] b) Determine the input and output resistances of Current Shunt feedback amplifier. [L4][CO2][6M] 4. a) Derive the expressions of input and output resistances for Voltage Shunt FBA. [L4][CO2][6M] b) Determine the input and output resistances of Current Series feedback amplifier. [L4][CO2][6M] 5. a) An amplifier has a voltage gain of 400, f 1 = 50 Hz, f 2 = 200kHz and a distortion of 10% without feedback. Determine the amplifier voltage gain, f 1f, f 2f and D f when a negative feedback is applied with feedback ratio of 0.01. b) A voltage series negative feedback amplifier has a voltage gain without feedback of A = 500, Electronic Circuit Analysis Page 5
input resistance R i = 3kΩ, output resistance R 0 = 20kΩ and feedback ratio β = 0.01. Calculate the voltage gain A f, input resistance R if, and output resistance R of of the amplifier with feedback. 6. a) State Barkhausen Criterion for oscillation. Explain the principle of operation of oscillator. b) Classify the different types of oscillators. [L1][CO2][6M] 7. a) Derive the expression for frequency of oscillations for RC phase shift Oscillator. [L4][CO2][6M] b) Discuss the working principle of Wein bridge oscillator and derive the expression for frequency of oscillations. 8. a) With neat diagram, explain Hartley Oscillator and derive its frequency of oscillation. b) Discuss Colpitts Oscillator and derive its frequency of oscillation. 9. a) Give the general analysis of an LC Oscillator. [L4][CO2][6M] b) Draw the equivalent circuit of a Quartz Crystal and explain its principle of operation with the help of neat circuit diagram. 10. a) Explain the concept of stability of Oscillators. b) In the Hartley oscillator, L 2 = 0.4mH and C = 0.004 µf. If the frequency of the oscillator is 120 khz, find the value of L 1. Neglect the mutual inductance. [L3][CO2][6M] UNIT V POWER AMPLIFIERS & TUNED AMPLIFIERS 1. a) With neat diagram explain Series fed, Directly coupled Class A Power Amplifier and derive its maximum efficiency. b) A series fed Class A amplifier shown if the Fig, operates from dc source and applied sinusoidal input signal generates peak base current 9mA. Calculate : (i) Quiescent current I CQ, (ii) Quiescent voltage V CEQ, (iii) DC input power P DC, (iv) AC output power P AC and (v) Efficiency. Electronic Circuit Analysis Page 6
2. a) Discuss with diagram, Transformer coupled Class A Power Amplifier and derive its maximum efficiency. b) Explain second harmonic distortion by three point method. 3. a) Describe Higher order harmonic distortion by five point method. [L1][CO2][6M] b) With neat diagram explain Push Pull Class B Power Amplifier and derive its maximum efficiency. 4. a) Describe Complementary Symmetry Class B Power Amplifier with diagram and write about crossover distortion in class B power amplifiers. [L1][CO2][6M] b) A class B push pull amplifier supplies power to a resistive load of 12Ω. The output transformer has a turns ratio of 3:1 and efficiency of 78.5%. Obtain (i) Maximum power output, (ii) maximum power dissipation in each transistor and (iii) Maximum base and collector current For each transistor. Assume h fe = 25 and V CC = 20V. 5. a) Write notes on Class AB operation. b) Discuss the need of Heat sink for power transistors. Mention about thermal stability of power transistors. 6. Describe the operation of a single tuned capacitive coupled amplifier with diagram and derive the expression for its centre frequency, Quality factor, Voltage gain and bandwidth. [L1][CO2][12M] 7. Discuss Double Tuned Amplifier with neat diagram and derive the expression for its bandwidth. [L2][CO2][12M] 8. a) Explain the effect of cascading single tuned amplifiers on bandwidth. b) The bandwidth of single tuned amplifier is 20kHz. Calculate the bandwidth if such three stages are cascaded. Also calculate the bandwidth for four stages. [L3][CO2][6M] 9. a) With circuit diagram, explain the stagger tuning operation. Give necessary graph. b) Explain the stability considerations of a tuned amplifier. 10. a) A single tuned RF amplifier uses a transistor with an output resistance of 50 KΩ, output capacitance of 15 pf and internal resistance of next stage is 20 kω. The tuned circuit consists of 47 pf capacitance in parallel with series combination of 1µH inductance and 2Ω resistance. Electronic Circuit Analysis Page 7
Calculate resonant frequency, effective quality factor and bandwidth of the circuit. b) Explain the advantages, disadvantages and applications of Tuned Amplifiers. Prepared by: 1. Dr. P.RATNA KAMALA Professor/ECE 2. Mr M. AFSAR ALI Professor/ECE Electronic Circuit Analysis Page 8