Rr210401 Electronic Circuits Analysis Feb 2008
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Set No. 1
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
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ss
.co
.in
1. Draw an ac equivalent circuit for amplifier shown in figure1. For the transistor assume hrb =0, hib =25Ω, hf b =-0.99 and hob =10−6 A/V. Derive and calculate Ai ,Avs , Ro and Ri . [16]
Figure 1
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m
2. (a) Draw the typical Hybrid π model for a transistor in the CE configuration. Derive the hybrid π conductances in CE configuration. (b) Show that the hybrid π model is valid for frequencies upto approximately fT /3. [8+8]
3. (a) Explain about different types of distortions that occur in amplifier circuits. (b) When 2-stages of identical amplifiers are cascaded, obtain the expressions for overall voltage gain, current gain and power gain. [6+10] 4. (a) Derive the expression for maximum collector Power Dissipation Pc(M ax) in the case of class B power amplifiers. What is its maximum value? (b) Explain the term Half wave symmetry.
[10+6]
5. (a) Draw the complementary - symmetry class-B power amplifier circuit with single power supply and explain its working . (b) In complementary - symmetry class-B power amplifier circuit, VCC =25 Volts; RL =16Ω and Imax =2 Amps. Determine the input power, output power and efficiency. [8+8] 1 of 2
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Set No. 1
Code No: RR210401 6. (a) Explain the working of single tuned amplifier.
(b) Derive the expression to obtain universal resonance curve and explain its significance in practical circuits? [6+10] 7. (a) What are the limitations of various Linear regulators. Explain.
.co
.in
(b) In the given Zener diode regulator circuit, Zener diode conducts if the supply voltage Vi is greater than 20V. Zener diode voltage is 16V. The meter resistance is 500 ohms. Find R1 and R2 where R1 + R2 = 99.5KΩ. {As shown in the Figure7b} [6+10]
ss
Figure 7b
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8. (a) Give the internal block schematic and pin configurations of 723 - voltage regulator.
se
(b) Draw circuit diagram of 7812 voltage regulator along with current boosting circuit and explain its operation. Derive expression for load current. [8+8]
ca
m
pu
⋆⋆⋆⋆⋆
2 of 2
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Set No. 2
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
re
ss
.co
.in
1. (a) Calculate voltage gain AV = VO /VS at 1kHz for the circuit shown Figure1a. FET parameters are gm =2mA/V and rd =10k. Neglect capacitances.
[8+8]
ca
m
Figure 1a (b) Repeat part (a) if capacitance 0.003µf is taken under consideration.
2. (a) What are the specifications of amplifiers? Explain them. Give their typical values. (b) The LF parameters of a transistor at Ic = 20mA, Vce = 10V and at room temperature hie = 400 Ω, hoe = 10 −5 A/V , hf e = 150, hre = 10−4 . At the same operating point fT = 60 MHz, and Cob = 3PF , compute the values of all the hybrid -π parameters. [6+10] 3. (a) Obtain the theoretical expressions for f1 n and f2 n when n-stages of identical amplifiers are cascaded. (b) For a given transistor (BJT), hf e = 100. fB = 5 KHzs. Determine the Bandwidth of the transistor. If the lower cut off frequency f1 = 100 Hzs and upper cut off frequency f2 = 100 KHzs, then determine the midband frequency f0 of the amplifier circuit. [10+6] 4. (a) In a class B amplifier VCEmin =1V and supply voltage Vcc is equal to 18V. Find the collector circuit efficiency. 1 of 2
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Set No. 2
Code No: RR210401
(b) Write a short note on power output and efficiency of power amplifiers. [8+8] 5. (a) Draw the complementary - symmetry class-B power amplifier circuit with single power supply and explain its working . (b) In complementary - symmetry class-B power amplifier circuit, VCC =25 Volts; RL =16Ω and Imax =2 Amps. Determine the input power, output power and efficiency. [8+8] 6. (a) Write down the expression for band width of a tuned circuit in terms of the quality factor and resonant frequency. (b) Explain the operation of a single tuned amplifier.
[10+6]
.in
7. (a) Draw the circuit of a series regulator circuit with discrete components and explain its operation. What are the limitations of a series regulator circuit?
.co
(b) Explain the working of a Zener regulator circuit and explain its working. [8+8] 8. (a) Draw the circuit of 7805 voltage regulator IC and explain its working.
re
ss
(b) Using 7805 IC voltage regulator, design current source to deliver 0.25A current to 48 ohms, 10 watts load. [8+8]
ca
m
pu
se
xp
⋆⋆⋆⋆⋆
2 of 2
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Set No. 3
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Sketch the circuit of a CS amplifier. Derive the expression for AV at low frequencies. What is the maximum value of AV ? (b) For the CE transistor amplifier circuit with Rs and RL , show that if RL = ∞ and Rs = 0. , if Rs = 0.
[8+8]
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Ro =
−hf e hie hoe − hre hf e −hie hie hoe − hre hf e
.in
i. (AV S )max =
ss
2. (a) Explain how the parameters of hybrid-π model varies with IC , VCE and temperature.
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(b) The hybrid-π parameters of the transistor used in circuit are : gm = 50mA/V, rbb′ =100Ω, 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} [6+10]
ca
m
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se
i. The upper 3 dB frequency of the current gain AI ii. The magnitude of voltage gain at the frequency of part (i).
Figure 2b 3. (a) The gain of an RC coupled 2 stage FET amplifier falls by 90% of the midband value at 400 kHz. If gm of each FET is 10 m A/V, and total output capacitance for each stage is 20 pF. Calculate the RL required and the midband gain of each stage (b) Write a short note on Bandwidth of amplifiers.
[10+6]
4. (a) Single ended power amplifier is not used in practical circuit. Instead a push pull amplifier is used. Why? (b) Draw a circuit diagram of a push pull amplifier circuit and explain
[6+10]
i. how proper biasing is achieved giving circuit. ii. how AC power free from even harmonics is developed across the load. 1 of 2
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Set No. 3
Code No: RR210401
5. (a) Explain the reasons for harmonic distortion in push pull power amplifiers. (b) Derive the expression for the power of output signal having distortion. (c) 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 =8Ω. Calculate the total harmonic distortion, fundamental power component and total power. [5+5+6] 6. (a) Write down the expression for band width of a tuned circuit in terms of the quality factor and resonant frequency. (b) Explain the operation of a single tuned amplifier.
[10+6]
7. (a) What are the limitations of unregulated power supplies?
.in
(b) Give schematic circuit diagram of a series voltage regulator circuit and explain its action and what are its limitations. [8+8]
.co
8. (a) Draw the circuit for 7805 voltage regulator along with unregulated power supply and explain its working.
re
ss
(b) Explain how 78XX can be used as a current source. Draw the circuit and explain. [8+8]
ca
m
pu
se
xp
⋆⋆⋆⋆⋆
2 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 4
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
re
ss
.co
.in
1. (a) Calculate voltage gain AV = VO /VS at 1kHz for the circuit shown Figure1a. FET parameters are gm =2mA/V and rd =10k. Neglect capacitances.
[8+8]
ca
m
Figure 1a (b) Repeat part (a) if capacitance 0.003µf is taken under consideration.
2. (a) Draw the typical Hybrid π model for a transistor in the CE configuration. Derive the hybrid π conductances in CE configuration. (b) Show that the hybrid π model is valid for frequencies upto approximately fT /3. [8+8] 3. (a) Explain about different methods of Inter stage coupling in amplifiers. (b) Two transistor amplifier circuits are cascaded as shown in figure3b. The hparameter values are as given under. Determine the overall voltage gain Av. hie =2.2k hie =1.8k
hf e =40 hre =5×10−4 hf e =-50 hre =1
hoe =25µ mho hoe =25µA/V [6+10]
1 of 2
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Set No. 4
Code No: RR210401
Figure 3b
.in
4. In a class A amplifier VCEmax =25 V, VCEmin =5 V. Find the overall efficiency for (a) series fed load
.co
(b) Transformer coupled load.
[8+8]
ss
5. (a) Discuss the effect of nonlinear region of iB -VBE characteristic of each transistor used in complementary - symmetry class-B power amplifiers in detail.
xp
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(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. [8+8]
se
6. (a) Explain the operation of a Double tuned amplifier. (b) Explain the advantages of double tuned circuit over single tuned circuit. [8+8]
pu
7. (a) Draw the circuit diagram of a series regulator circuit and explain its operation.
m
(b) Explain with the help of circuit diagram. How short circuit/overload protection circuit will work. [8+8]
ca
8. (a) List out the limitations of three terminal voltage regulator circuits. (b) Draw the circuit of 3 terminal voltage regulator to use it as a current source and explain its operations. (c) What are the advantages of switched mode power supplies over linear voltage Regulators [5+5+6] ⋆⋆⋆⋆⋆
2 of 2
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Set No. 1
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
re
ss
.co
.in
1. Draw an ac equivalent circuit for amplifier shown in figure1. For the transistor assume hrb =0, hib =25Ω, hf b =-0.99 and hob =10−6 A/V. Derive and calculate Ai ,Avs , Ro and Ri . [16]
Figure 1
ca
m
2. (a) Draw the typical Hybrid π model for a transistor in the CE configuration. Derive the hybrid π conductances in CE configuration. (b) Show that the hybrid π model is valid for frequencies upto approximately fT /3. [8+8]
3. (a) Explain about different types of distortions that occur in amplifier circuits. (b) When 2-stages of identical amplifiers are cascaded, obtain the expressions for overall voltage gain, current gain and power gain. [6+10] 4. (a) Derive the expression for maximum collector Power Dissipation Pc(M ax) in the case of class B power amplifiers. What is its maximum value? (b) Explain the term Half wave symmetry.
[10+6]
5. (a) Draw the complementary - symmetry class-B power amplifier circuit with single power supply and explain its working . (b) In complementary - symmetry class-B power amplifier circuit, VCC =25 Volts; RL =16Ω and Imax =2 Amps. Determine the input power, output power and efficiency. [8+8] 1 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 1
Code No: RR210401 6. (a) Explain the working of single tuned amplifier.
(b) Derive the expression to obtain universal resonance curve and explain its significance in practical circuits? [6+10] 7. (a) What are the limitations of various Linear regulators. Explain.
.co
.in
(b) In the given Zener diode regulator circuit, Zener diode conducts if the supply voltage Vi is greater than 20V. Zener diode voltage is 16V. The meter resistance is 500 ohms. Find R1 and R2 where R1 + R2 = 99.5KΩ. {As shown in the Figure7b} [6+10]
ss
Figure 7b
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re
8. (a) Give the internal block schematic and pin configurations of 723 - voltage regulator.
se
(b) Draw circuit diagram of 7812 voltage regulator along with current boosting circuit and explain its operation. Derive expression for load current. [8+8]
ca
m
pu
⋆⋆⋆⋆⋆
2 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 2
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
re
ss
.co
.in
1. (a) Calculate voltage gain AV = VO /VS at 1kHz for the circuit shown Figure1a. FET parameters are gm =2mA/V and rd =10k. Neglect capacitances.
[8+8]
ca
m
Figure 1a (b) Repeat part (a) if capacitance 0.003µf is taken under consideration.
2. (a) What are the specifications of amplifiers? Explain them. Give their typical values. (b) The LF parameters of a transistor at Ic = 20mA, Vce = 10V and at room temperature hie = 400 Ω, hoe = 10 −5 A/V , hf e = 150, hre = 10−4 . At the same operating point fT = 60 MHz, and Cob = 3PF , compute the values of all the hybrid -π parameters. [6+10] 3. (a) Obtain the theoretical expressions for f1 n and f2 n when n-stages of identical amplifiers are cascaded. (b) For a given transistor (BJT), hf e = 100. fB = 5 KHzs. Determine the Bandwidth of the transistor. If the lower cut off frequency f1 = 100 Hzs and upper cut off frequency f2 = 100 KHzs, then determine the midband frequency f0 of the amplifier circuit. [10+6] 4. (a) In a class B amplifier VCEmin =1V and supply voltage Vcc is equal to 18V. Find the collector circuit efficiency. 1 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 2
Code No: RR210401
(b) Write a short note on power output and efficiency of power amplifiers. [8+8] 5. (a) Draw the complementary - symmetry class-B power amplifier circuit with single power supply and explain its working . (b) In complementary - symmetry class-B power amplifier circuit, VCC =25 Volts; RL =16Ω and Imax =2 Amps. Determine the input power, output power and efficiency. [8+8] 6. (a) Write down the expression for band width of a tuned circuit in terms of the quality factor and resonant frequency. (b) Explain the operation of a single tuned amplifier.
[10+6]
.in
7. (a) Draw the circuit of a series regulator circuit with discrete components and explain its operation. What are the limitations of a series regulator circuit?
.co
(b) Explain the working of a Zener regulator circuit and explain its working. [8+8] 8. (a) Draw the circuit of 7805 voltage regulator IC and explain its working.
re
ss
(b) Using 7805 IC voltage regulator, design current source to deliver 0.25A current to 48 ohms, 10 watts load. [8+8]
ca
m
pu
se
xp
⋆⋆⋆⋆⋆
2 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 3
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Sketch the circuit of a CS amplifier. Derive the expression for AV at low frequencies. What is the maximum value of AV ? (b) For the CE transistor amplifier circuit with Rs and RL , show that if RL = ∞ and Rs = 0. , if Rs = 0.
[8+8]
.co
Ro =
−hf e hie hoe − hre hf e −hie hie hoe − hre hf e
.in
i. (AV S )max =
ss
2. (a) Explain how the parameters of hybrid-π model varies with IC , VCE and temperature.
xp
re
(b) The hybrid-π parameters of the transistor used in circuit are : gm = 50mA/V, rbb′ =100Ω, 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} [6+10]
ca
m
pu
se
i. The upper 3 dB frequency of the current gain AI ii. The magnitude of voltage gain at the frequency of part (i).
Figure 2b 3. (a) The gain of an RC coupled 2 stage FET amplifier falls by 90% of the midband value at 400 kHz. If gm of each FET is 10 m A/V, and total output capacitance for each stage is 20 pF. Calculate the RL required and the midband gain of each stage (b) Write a short note on Bandwidth of amplifiers.
[10+6]
4. (a) Single ended power amplifier is not used in practical circuit. Instead a push pull amplifier is used. Why? (b) Draw a circuit diagram of a push pull amplifier circuit and explain
[6+10]
i. how proper biasing is achieved giving circuit. ii. how AC power free from even harmonics is developed across the load. 1 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 3
Code No: RR210401
5. (a) Explain the reasons for harmonic distortion in push pull power amplifiers. (b) Derive the expression for the power of output signal having distortion. (c) 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 =8Ω. Calculate the total harmonic distortion, fundamental power component and total power. [5+5+6] 6. (a) Write down the expression for band width of a tuned circuit in terms of the quality factor and resonant frequency. (b) Explain the operation of a single tuned amplifier.
[10+6]
7. (a) What are the limitations of unregulated power supplies?
.in
(b) Give schematic circuit diagram of a series voltage regulator circuit and explain its action and what are its limitations. [8+8]
.co
8. (a) Draw the circuit for 7805 voltage regulator along with unregulated power supply and explain its working.
re
ss
(b) Explain how 78XX can be used as a current source. Draw the circuit and explain. [8+8]
ca
m
pu
se
xp
⋆⋆⋆⋆⋆
2 of 2
http://www.campusexpress.co.in
campusexpress.co.in
Set No. 4
Code No: RR210401
II B.Tech I Semester Supplimentary Examinations, February 2008 ELECTRONIC CIRCUITS ANALYSIS (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
pu
se
xp
re
ss
.co
.in
1. (a) Calculate voltage gain AV = VO /VS at 1kHz for the circuit shown Figure1a. FET parameters are gm =2mA/V and rd =10k. Neglect capacitances.
[8+8]
ca
m
Figure 1a (b) Repeat part (a) if capacitance 0.003µf is taken under consideration.
2. (a) Draw the typical Hybrid π model for a transistor in the CE configuration. Derive the hybrid π conductances in CE configuration. (b) Show that the hybrid π model is valid for frequencies upto approximately fT /3. [8+8] 3. (a) Explain about different methods of Inter stage coupling in amplifiers. (b) Two transistor amplifier circuits are cascaded as shown in figure3b. The hparameter values are as given under. Determine the overall voltage gain Av. hie =2.2k hie =1.8k
hf e =40 hre =5×10−4 hf e =-50 hre =1
hoe =25µ mho hoe =25µA/V [6+10]
1 of 2
http://www.campusexpress.co.in
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Set No. 4
Code No: RR210401
Figure 3b
.in
4. In a class A amplifier VCEmax =25 V, VCEmin =5 V. Find the overall efficiency for (a) series fed load
.co
(b) Transformer coupled load.
[8+8]
ss
5. (a) Discuss the effect of nonlinear region of iB -VBE characteristic of each transistor used in complementary - symmetry class-B power amplifiers in detail.
xp
re
(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. [8+8]
se
6. (a) Explain the operation of a Double tuned amplifier. (b) Explain the advantages of double tuned circuit over single tuned circuit. [8+8]
pu
7. (a) Draw the circuit diagram of a series regulator circuit and explain its operation.
m
(b) Explain with the help of circuit diagram. How short circuit/overload protection circuit will work. [8+8]
ca
8. (a) List out the limitations of three terminal voltage regulator circuits. (b) Draw the circuit of 3 terminal voltage regulator to use it as a current source and explain its operations. (c) What are the advantages of switched mode power supplies over linear voltage Regulators [5+5+6] ⋆⋆⋆⋆⋆
2 of 2
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