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ELECTRONIC CIRCUIT

ANALYSIS

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MALLAREDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTROINICS AND COMMUNICATION ENGINEERING

B.TECH II YEAR II SEMESTER EXAMINATIONS-2015

ELECTRONIC CIRCUIT ANALYSIS

MODEL PAPER I MAX MARKS: 75

Answer all the following questions:

PART A:

1. (a) Define h-parameters of a transistor in a small signal amplifier. What are the benefits of h-parameters? (2Marks)

b) Give the advantages of the Darlington Amplifier circuit. (2Marks)

c) 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. (3 Marks) d) Draw the hybrid-π equivalent of a CE transistor valid for high frequency (3Marks) e) Explain the classification of power amplifiers based on class of operation (2Marks) f) Write the applications of tuned amplifiers? (3Marks) g) Justify that Crystal oscillators are more stable than other Oscillators. (2Marks) h)What are the characteristics of Negative feedback Amplifiers? (3Marks) i)explain about the the types of Distortions in Amplifiers. (2Marks) j)Explain why even harmonics are cancelled out in Push Pull Amplifiers? (3Marks)

PART B: 5*10=50M

2)(a) Draw the circuit of an emitter follower, and derive the expressions for AI, Av, Ri, R0 in terms of CE parameters. (b) State and explain Miller’s theorem and its dual. (OR) 3) (a) Derive the expression for bandwidth, and write the expression for rise time for the band pass of cascaded stages. (b) Analysis for CE amplifier with emitter resistance 4) a)Draw and explain the small signal model of a MOS amplifier. b) Derive the expression for the voltage gain of a MOS-Source Follower. (OR)

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5)Draw the hybrid-pi model of a Transistor in CE configuration and and derive the conductance and capacitances. 6.a) Explain and justify the effect of Negative feedback on the characteristics of an amplifier. b) An amplifier with open loop gain of 2000±150 is available. It is necessary to have the amplifier whose voltage gain varies by not more than ±0.2%. Calculate the feedback factor β, and the gain of the amplifier with feedback. [10+5] (OR) 7). Derive the expression for the frequency of oscillations of a BJT-RC Phase shift Oscillator. 8(a) How even harmonics is eliminated using push-pull circuit, derive the expression. (b) Write about the operation of a class D amplifier (OR) 9(a) What is the drawback of class B amplifier. How it is going to be overcome using class AB Amplifier with neat diagram. (b) Write about the operation of a class D amplifier. 10 (a) Derive the expression for bandwidth in terms of resonant frequency and quality factor in case of double tuned amplifiers. (b) Differentiate between synchronous tuned amplifiers and tapped tuned amplifiers. (OR) 11) Write notes on the following: a) Stagger Tuning b) Single Tuned and Double Tuned Amplifiers.

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MALLAREDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTROINICS AND COMMUNICATION ENGINEERING

B.TECH II YEAR II SEMESTER EXAMINATIONS-2015

ELECTRONIC CIRCUIT ANALYSIS

MODEL PAPER II MAX MARKS: 75

Answer all the following questions:

PART A:

1. a State and explain Millers Theorem and its dual. (2Marks)

b) Obtain the theoretical expressions for f1n and f2n when n-stages of identical amplifiers are cascaded. (3Marks)

c) Explain the choice of configuration in a cascade of Amplifiers. (2Marks)

d) Draw Hybrid - π model for a transistor in the CE configuration (3Marks)

e) What is Negative feedback? Discuss how it can improve stability in an Amplifier. (3Marks)

f)Draw the electrical model of a Piezo electric Crystal and explain how it works as a fixed frequency oscillator. (2Marks)

g)Define Conversion efficiency. Determine the maximum value of Conversion efficiency for a series fed Class-A Power Amplifier. (3 Marks) h) In series fed Class - A power amplifier, explain the importance of the position of operating point on output signal swing. Show that the conversion efficiency is 25%. (2Marks) i)What are the limitations of stagger tuned Amplifiers? (3Marks) j) Explain the reasons for oscillations in a tuned amplifier. (2Marks)

PART B: 5*10=50M

2) Write the analysis of a CE amplifier circuit using h parameters. Derive the expressions for AI, AV, Ri, R0, AIs, AVs. (OR) 3)A two-stage amplifier circuit in a CE-CC configuration. The transistor parameters at the corresponding quiescent points are hie=1KΩ, hre=10-4, hfe=50, hoe=10-4 A/V. hic=1KΩ,

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hrc=1, hfc= -51, hoc=10-4 A/V. Find the input and output impedances and individual, as well as overall, voltage and current gains. 4) a) Derive the expression for the CE short-circuit current gain Ai as a function of frequency. (b) Define fβ and fT. Find the current gain with resistive load. (OR) 5) a)The figure shown below uses an N-channel FET having Idss=2mA,Vp= -2v.If the quiescent Drain to Gate voltage is 10 v, find R1 and the input impedance.

b) Derive the expression for the Current gain of a MOS-Common Gate Amplifier. 6)a)Derive the expression for frequency of Oscillation for a Colpitts Oscillator. b)In a A Hartley Oscillator L2=0.04mH,C=0.004UH.If the frequecny of Oscillation is 150 kHz,find L1.neglect mutual Inductance. (OR) 7a) Explain and justify the effect of Negative feedback on the characteristics of an amplifier. b) An amplifier with open loop gain of 2000±150 is available. It is necessary to have the amplifier whose voltage gain varies by not more than ±0.2%. Calculate the feedback factor β, and the gain of the amplifier with feedback.

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8a)Show that even harmonics cancel out and overall distortion is reduced in a push pull configuration . b)Compare series fed and Transformer coupled Class A Amplifiers. (OR) 9a) Discuss the effect of nonlinear region of iB-VBE characteristic of each transistor used in complementary - symmetry class-B power amplifiers in detail. (b) The power amplifier supplies 4 watts for 8 ohms load. The zero-signal d.c.Collector current is 35mA and it rises to 40mA when the signal is applied.Determine the percent second harmonic distortion. 10) Draw and explain the circuit diagram and operation of a double tuned amplifier and explain how it is different from a single tuned amplifier. Also explain different stages of simplification of the equivalent circuit of a double tuned amplifier?

11(a) what is a Stagger tuned amplifier? Draw the circuit diagram of it and explain its working? (b) Derive the overall gain function and also draw its frequency response?

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MALLAREDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTROINICS AND COMMUNICATION ENGINEERING

B.TECH II YEAR II SEMESTER EXAMINATIONS-2015

ELECTRONIC CIRCUIT ANALYSIS

MODEL PAPER III MAX MARKS: 75

Answer all the following questions:

PART A:

1a) List the sailent features of cascade and Darlington pair? (2Marks)

b) Explain about different methods of Inter stage coupling in amplifiers. (3Marks)

c) Prove that hie=rbb’ +rb’e. (2Marks)

d) What is the effect of bypass capacitors on the bandwidth of an amplifier? (2Marks)

e) Derive the expression for voltage gain for Cs amplifier with resistive load? (3Marks)

f) What do u meant by voltage amplifier and Current amplifier? (2Marks)

g) Single ended power amplifier is not used in practical circuit. Instead a push pull amplifier is used. Why? (3Marks)

h) With the help of general block diagram explain the term feedback (2Marks)

i) Explain the classification of Oscillators. (3Marks)

j) Write a short notes on Class D Amplifier. (2Marks)

PART B: 5*10=50M

2)Two transistor amplifier circuits are cascaded as shown in the figure shown belowThe h-parameter values are as given under. Determine the overall voltage gain Av.hie=2.2k hfe=40 hre=5×10−4 hoe=25μ mho hie=1.8k hfe=-50 hre=1 hoe=25μA/V

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]

(OR)

3a) With the help of necessary equations, discuss the variation of AI ,AV ,Ri, and Ro with RS and RL in Common Emitter configuration. b) For a CE configuration, what is the maximum value of RS for which Ro differs by no more than 10 percent of its value for RS = 0. The h-parameter values are hfe = 50, hie =1.1K, hre = 2.5x10−4, hoe = 25 μA/V.

4a) Sketch the circuit of a CS amplifier. Derive the expression for AV at low frequencies. What is the maximum value of AV ?

b)Calculate voltage gain AV = VO/VS at 1kHz for the circuit shown Figure1a. FET parameters are gm=2mA/V and rd =10k. Neglect capacitances.

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(OR)

5a) Explain how the parameters of hybrid-π model varies with IC, VCE and tem- perature. (b) The hybrid-π parameters of the transistor used in circuit are : gm = 50mA/V, rbb′=100, rb′e= 1K, rb′c = 4M, rce = 80K, Cc = 3PF, Ce = 100 PF. Using Miller’s theorem and the appropriate analysis, compute {As shown in the Figure2b} i. The upper 3 dB frequency of the current gain AI ii. The magnitude of voltage gain at the frequency of part (i)

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6a) Explain why RC Oscillators are preferred for low frequencies?

Draw a neat Circuit diagram of Phase Shift Oscillator using BJT and derive the expression for minimum hfe required to sustain oscillations.

(OR)

7a) Draw the circuit diagram of a current series feedback and derive expressions for Voltage gain and output resistance and input resistance .

b) Show that Voltage shunt feedback amplifier transresistance gain, Ri, Ro are decreased by a factor (1+Aβ) with feedback.

8a)In a class A amplifier VCEmax=25 V, VCEmin=5 V. Find the overall efficiency for (a) series fed load (b) Transformer coupled load.

(OR)

9a) Draw a circuit diagram of a push pull amplifier circuit and explain how proper biasing is achieved giving circuit. Also explain how AC power free from even harmonics is developed across the load. b) For harmonic distortions of D2=0.1; D3=0.02 and D4=0.01 with fundamental component of output signal I1=4 A and RL=8. Calculate the total harmonic distortion, fundamental power component and total power.

10a) a) Derive the expression for bandwidth in terms of resonant frequency and quality factor in case of double tuned amplifiers. (10) (b) Differentiate between synchronous tuned amplifiers and tapped tuned amplifiers.

(OR)

11(a) What is synchronous tuning ? Derive an expression for bandwidth of an n- stage synchronously tuned amplifier? (b) Show that for an ‘n’ stage synchronously tuned amplifier, maximum. band- width is obtained when the single stage gain is 4.34dB.

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MALLAREDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTROINICS AND COMMUNICATION ENGINEERING

B.TECH II YEAR II SEMESTER EXAMINATIONS-2015

ELECTRONIC CIRCUIT ANALYSIS

MODEL PAPER IV MAX MARKS: 75

Answer all the following questions:

PART A:

1a) Compare between CB, CC and CE amplifiers. (2Marks)

b) What is Darlington connection? (3Marks)

c) Prove that hfe=gmrb’e (2Marks)

d) Sketch the circuit of a CS amplifier and explain its working. (3Marks)

e) What is harmonic distortion? (2Marks)

f) Give the topology for various feedback amplifiers? (2Marks)

g) What is meant by Positive feedback? What is meant by Barkhausen Creiterian?Explain. (3 Marks)

h) Explain the classification of power amplifiers with respect to selection of Q point. (2Marks)

i) Discuss advantages and disadvantages of tuned amplifiers. (3Marks)

j) What is stagger Tuning? (2Marks)

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PART B: 5*10=50M

2a) (a) Discuss about different types of distortions that occur in amplifier circuits (b) Three identical non interacting amplifier stages in cascade have an overall gain of 1 dB down at 30 Hz compared to mid band. Calculate the lower cutoff frequency of the individual stages.

(OR)

3) A two-stage amplifier circuit (CE-CC configuration) is shown in figure. The h- parameter values are hfe = 50, hie=2 K , hre =6× 10−4, hoe = 25μA/V.hfc = -51, hic =2 K, hrc = 1, hoc = 25μ A/V. Find the input and output impedances and individual, as well as overall voltage and current gains.

4a) What are the typical values of various components in Hybrid - π model? Show that at low frequencies the Hybrid - π model with rb′e and rce taken as infinite reduces to the approximate CE h- parameter model. (b) The following low- frequency parameters are known for a given transistor at IC = 10mA, VCE =10 V, and at room temperature, hie = 500 hoe = 4x10−5 A/V hfe = 100 hre = 10−4. At the same operating point, fT = 50MHz and Cc=3PF, compute the values of all the Hybrid - π parameters

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(OR)

5a) Draw and explain the small signal model of a MOS amplifier. b) Derive the expression for the voltage gain of a common source FET Amplifier.

6a)Derive an expression for transfer gain of a feedback amplifier.

b)The feedback amplifier shown has transistor parameters hie= 1k, hre and hoe negligible. Find Rmf=Vo/Is Avf=Vo/VsRif and Rof.

(OR)

7a) Explain why negative feedback is employed in Wien Bridge Oscillators?

b)Derive the expression for frequency of oscillation of a Wien Bridge Oscillator.

8a) Explain the reasons for harmonic distortion in push pull power amplifiers. (b) Derive the expression for the power of output signal having distortion.

(OR)

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9a) Discuss the effect of nonlinear region of iB-VBE characteristic of each transistor used in complementary - symmetry class-B power amplifiers in detail. (b) The power amplifier supplies 4 watts for 8 ohms load. The zero-signal d.c.Collector current is 35mA and it rises to 40mA when the signal is applied.Determine the percent second harmonic distortion.

10a) (a) Draw and explain the circuit diagram of a single tuned Capacitance coupled amplifier. Also explain its operation? (b) Draw and explain the significance of Gain versus Frequency curve of tuned amplifiers when they are used in radio amplifiers? (c) Draw the Ideal and actual frequency response curves of a single tuned ampli- fier?

(OR)

11a) Explain the operation of a Double tuned amplifier. b) Explain the advantages of double tuned circuit over single tuned circuit.

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MALLAREDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTROINICS AND COMMUNICATION ENGINEERING

B.TECH II YEAR II SEMESTER EXAMINATIONS-2015

ELECTRONIC CIRCUIT ANALYSIS

MODEL PAPER V MAX MARKS: 75

Answer all the following questions:

PART A: 1a) List benefits of h –parameters. (3Marks) b) If eight identical amplifiers are cascaded each having fh =200 KHz, determine the overall upper 3dB frequency fh. Assume non interacting stages. (3Marks) c)Derive the expression for the gain bandwidth product of a Transistor. (2Marks) d)State the advantages and disadvantages of a Source follower circuit. (3Marks) e)What are the advantages and disadvantages of negative feedback. (2 Marks) f)Derive the expressions for fβ and fT . (3Marks) g)Explain sampling and mixing networks. (2Marks) h)Explain the classification of feedback oscillators. (2Marks) i)What is a heatsink? What is its function? (3Marks) j)Explain about the importance of neutralization techniques. (2Marks)

PART-B: 5*10=50 M

2a) . (a) Draw the circuit diagram of CB- amplifier and its h-parameter equivalent circuit. List out the characteristics of a CB amplifier. (b) In a single stage CB amplifier circuit, RE = 20K,RC = 10K, VEE = −20V, VCC = 20V,RL = 10KandRS = 0.5K. Find AI ,Ri,Ro,AV .

(OR)

3) A two-stage amplifier circuit (CE-CC configuration) is shown in figure. The h- parameter values are hfe = 50, hie=2 K , hre =6× 10−4, hoe = 25μA/V.hfc = -51, hic =2 K, hrc = 1, hoc = 25μ A/V.Find the input and output impedances and individual, as well as overall voltage

and current gains.

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(OR)

4a)Draw and explain the small signal equivalent for an emitter follower at high frequencies and obtain the voltage gain

b)Derive the expression for the CE short circuit current gain Ai with resistive load.

(OR)

5a)Explain the operation of Common Gate Amplifier with the help of a circuit diagram.

b)Draw the small signal equivalent of a MOS Amplifier.

6)Derive the expressions for Av, Zi , Zo, Ai of a voltage shunt feedback Amplifier.

(OR)

7)Derive the expressions for frequency of oscillation and condition for sustaining the oscillations for a Colpitts Oscillator.

8a) Explain the reasons for harmonic distortion in push pull power amplifiers. (b) Derive the expression for the power of output signal having distortion.

(OR)

9a) Discuss the effect of nonlinear region of iB-VBE characteristic of each transistor

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used in complementary - symmetry class-B power amplifiers in detail. (b) The power amplifier supplies 4 watts for 8 ohms load. The zero-signal d.c. Collector current is 35mA and it rises to 40mA when the signal is applied. Determine the percent second harmonic distortion.

(OR)

10) Explain the reasons for oscillations in a tuned amplifier. Briefly explain the methods used to stabilize the tuned amplifiers against oscillations?

(OR)

11a) Explain the operation of a Double tuned amplifier. b) Explain the types of neutralization with neat sketches.

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PULSE AND DIGITAL

CIRCUITS