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QUESTION BANK
EC6304-ELECTRONIC CIRCUITS I
III Semester
UNIT-I Power Supplies and Biasing of Discrete BJT and MOSFET
PART-A
1. What is Biasing and state the need for biasing. [MAY/JUN-09,13]
2. Define current amplification factor?
3. What is d.c load line? MAY/JUN-12]
4. Define stability factor?[ NOV/DEC-09,12]
5. What are the methods for biasing? NOV/DEC-09,12]
6. Why is the operating point selected at the Centre of the active region? [NOV/DEC 07]
7. What are the advantages of fixed bias circuit?
8. Give the expression for stability factor.[MAY-07,08]
9. What is the necessary of the coupling capacitor?
10. When does a transistor act as a switch?
11. List out the different types of biasing.
12. Define the stability factors S, S’ and S’’. [MAY-07,08]
13. What do you meant by thermal runway? [NOV/DEC-06]
14. Why FET is known as voltage variable resistor?[DEC-06]
15. What is meant by compensation techniques? [NOV/DEC-11]
16. List out the importance of selecting the proper operating point. (May-15)
17. What is bias compensation using thermistor
18. Why is temperature compensation required?
19. Calculate the value of feedback resistor required to self bias N –JFET with IDss=40mA,
Vp= -10V and VGSQ= -5 V.(May 10)
20. [MAY-15]
21. List the different types of FET biasing circuit. (May 12)
22. What is operating point?
23. What are the advantages of self bias circuit?
24. Find IB and IC if hFE=100, VBE=0.7V
[Nov 14]
25. What are the operating regions of N channel MOSFET and how to identify
the operating regions. [Nov 14]
PART-B
1. Explain the voltage divider bias method & derive an expression for stability factors.
2. Why biasing is necessary in BJT amplifier? Explain the concept of DC & AC load line
with neat diagram. How will you select the operating point, explain it using CE amplifier
characteristics?
3. Explain the collector feedback bias amplifier & derive an expression for stability factors.
4. Explain the fixed bias method & derive an expression for stability factors.
5. Derive stability factor S,S’ and S”of self biasing of BJT.( NOV-15)
6. Explain about common source self- bias & voltage divider bias for FET.
7. Explain in details about biasing FET.(DEC 11)
8. Discuss the various types of bias compensation.
9.
10.AU NOV 09
11.
12.
13.
14.
15.
16.
17.
18.The fixed bias circuit as shown in figure is subjected to an increase in junction temperature
from 25oC to 75oC. If β is 125 at 75oC. Determine the percentage change in Q point values
(Vce, Ic) over temperature change. Neglect any change in VBE.
19.A self bias circuit has RE=1 kΩ, R1=130 kΩ, R2=10 kΩ. If Vcc and Rc are adjusted to give
Ic=1mA at 10oC. Calculate the variation in Ic over temperature change of 10oC to 100oC. The
transistor used has the parameters given below,
Parameters
Ico (µA)
VBE(v)
β
10oC
0.01
0.74
60
100oC
1.2
0.54
140
20.Design a collector to base bias circuit to have operating point (10v, 4mA). The circuit is
supplied with 20v and uses a silicon transistor of hfe is 250.
21.Design a voltage divider bias circuit for the specified conditions. VCC=12v, VCE=6v,
IC=1mA, S=20, β=100 and VE=1v.
22. AU- May-15
23. Design Emitter bias for BJT with Ic=2mA, Vcc=18V,VCE=10V and β=150.( NOV-15)
24. Design voltage divider bias circuit for NMOS such that IDQ = 400µA, VDD = 14V,
Vds=2.3 V, Kn=1mA/V2 ,Vt= 1V. Assume a current of 1 µA through R1 and R2
and Vs=1.2 V . ( NOV-15)
25.Explain different types of biasing. (DEC- 06)
26. Explain the method of stabilizing the Q point. (Dec 12)
27. Explain in details about biasing methods of JFET.
28.Explain common source self bias and voltage divider bias for FET. .(DEC 12)
29. Sketch the bias circuit for enhancement MOSFET and explain its operation .(DEC 13)
30.Explain the working principle of Full wave Rectifier and derive the expression of ripple
factor, rectifier efficiency VRMS, IRMS Vdc and Idc.
31. Explain the working principle of Half wave Rectifier and derive the expression of ripple
factor, rectifier efficiency VRMS, IRMS Vdc and Idc.
Unit II-BJT Amplifiers
PART -A
1. Define CMRR of differential amplifier and how to improve it [MAY ‘15]
2. Why hybrid parameters are called so? Define them. [May-2007]
3. Draw a CE amplifier and its hybrid equivalent circuit. [May-2008]
4. Define Miller effect input capacitance.[Dec-2006, Dec2007, May-2008]
5. What is the need of differential amplifier?[Nov/Dec-2009] [ APR/MAY-11]
6. Why RE is replaced by a constant current bias in a differential amplifier?[Dec-2008]
7. State the various methods of improving CMRR. [Dec-2007]
8.[AU May 15]
9.Why emitter bypass capacitor CE is used in CE amplifier circuit. [APR/MAY 2004]
10.What are the salient features of hybrid parameters?
11.Mention the applications of class C amplifiers[APR/MAY-10,11]
12.What is crossover distortion? [APR/MAY-10,11]
13.How crossover distortion is eliminated?[MAY -2003, MAY-2006, MAY-2007]
14.what is the theoretical maximum conversion efficiency of class A power amplifier
[ APR/MAY-12][NOV/DEC-09]
15.Draw the circuit diagram of transformer coupled class A amplifier [NOV/DEC-06]
16.Why class ‘A’ amplifier must not be operated under no signal conditions. [DEC-2005]
17.What is class D amplifier? [ APR/MAY-13]
18.What are advantages and disadvantages of class B amplifier? [DEC-2004]
19.How do you bias the class A operation? [DEC-2005]
20.What is meant by Power amplifier? [DEC-2005]
21.List the features of Power amplifier.
22.If CMRR of differential amplifier 100dB ,find common mode gain if differential gain is
1000. [May 15]
23.What are the drawbacks of the transformer coupled amplifier? [ APR/MAY-11]
24. List the advantages of transformer coupled amplifier. [ APR/MAY-11]
25. Define the various h-parameters? [ May-2006, Dec-2008]
26. What does bootstrapping mean?.
PART-B
1. Explain the method to increase the input resistance using Darlington connection
[May’15]
2. Derive CMRR of differential amplifier with its equivalent circuit.[Nov 14]
3. Explain operation of cascode amplifier and derive its gain, input impedance and output
Impedance.
4.
5. [MAY-15]
6.
7.
8.
9.
10.
11.
12.
13. Draw the circuit diagram for an emitter coupled differential amplifier using BJT.[Dec 09]
14. Derive the expression of Ri and voltage gain for CE Amplifier with bypassed unbypassed
RE.
15. Draw and explain the hybrid π equivalent circuit for NPN transistor considering early effect.
16.
.
17.
18.Explain transformer coupled Class B power Amplifier.
19. Derive the expression of Ri and voltage gain for CB Amplifier and draw its hybrid model.
20. Derive the expression of Ri and voltage gain for CC Amplifier.
UNIT III
JFET AND MOSFET AMPLIFIERS
PART –A
1.
2.
3.
4.
5.
6.
Compare between JFET and MOSFET Amplifiers. [May ‘15]
What is meant by small signal?
What is the physical meaning of small signal parameter ro?
Write the equation for small signal condition that must be satisfied for linear amplifiers.
Draw the small signal equivalent circuit for common source NMOS Amplifier.
[May ‘15]
7. Draw the small signal model of common drain amplifier?
8. Draw the source follower amplifier circuit.
9. List the applications of MOSFET amplifiers.
10. Compare the characteristics of three MOSFET amplifier configurations.
11. Draw the small signal equivalent JFET common source circuit.
12. How does a transistor width-to-length ratio affect the small signal voltage gain of a common
source amplifier?
13. How a MOSFET can be used to amplify a time varying voltage?
14. How does body effect change the small signal equivalent of the MOSFET?
15. Why in general the magnitude of the voltage gain of a common source amplifier relatively
small?
16. What is voltage swing limitation?
17. What is the general condition under which a common gate amplifier would be used?
18. State the general advantage of using transistors in place of resistors in integrated circuits.
19. Give one reason why a JFET might be used as an input device in a circuit as proposed to a
MOSFET.
20. What are features of BIMOS cascode amplifiers? [NOV 14]
21. Draw the small signal of JFET Amplifier.[Nov 14]
22. What are the applications of BiCMOS?
23. Draw the characteristics of JFET and mark its regions of operation.
24. Draw the small signal model of CS,CD,CG of JFET Amplifier
25. Draw the small signal model of MOSFET
PART –B
1. Describe the operation and analyze the basic JFET amplifier circuits.
2. Derive gain, input and output impedance of common source JFET amplifier with neat circuit
diagram and equivalent circuit. [Nov 14]
3. Derive the small signal analysis of common source amplifier.
4. Derive gain, input and output impedance of source follower MOSFET amplifier with neat
circuit diagram and equivalent circuit. [Nov 14]
5. Derive the expression for voltage gain of common drain amplifier under small signal low
frequency conditions.
6.
Apply the MOSFET small signal equivalent circuit in the analysis of multistage amplifier
circuits.
7.
Explain common source amplifier with source resistor and source bypass capacitor.
8. Write short notes Voltage swing limitations, general conditions under which a source
follower amplifier would be used.
9.. Describe the characteristics of and analyze BiCMOS circuits.
10. Develop a small signal model of JFET device and analyze basic JFET amplifiers.
11. Explain graphically the amplification process in a simple MOSFET amplifier circuit.
12. Describe the small signal equivalent circuit of the MOSFET and determine the values of
small signal parameters?
13. Sketch the small signal high frequency circuit of a common source amplifier & derive the
expression for a voltage gain, input & output admittance and input capacitance.
14. Sketch a simple source-follower amplifier circuit and discuss the general ac circuit
characteristics.
15. Characterize the voltage gain and output resistance of a common-gate amplifier.
16. Derive the expression for voltage gain for PMOS source follower amplifier.
17. Draw the small signal equivalent of NMOS -CS, CD,CG configurations. Derive its voltage
gain.
18.
19.
20.
21..Draw small signal equivalent for the circuit shown below and calculate voltage gain.
22. [May ‘15]
Unit IV- Frequency Analysis of BJT and MOSFET Amplifiers
PART-A
1. Draw the frequency response curve of an amplifier.
2. What is the bandwidth of an amplifier? (NOV/DEC-11)
3. Define rise time.
4. Draw the hybrid π equivalent circuit of BJTs.(Dec 11)
5. What kind of techniques required increasing the input impedance?
6. Give relation between rise time and bandwidth.
7. Discuss the effect of bypass capacitor on frequency response of amplifier.
8. Give the main reason for the drop in gain at the low frequency region & high frequency
region.
9. If the rise time of BJT is 40nS, what is the bandwidth that can be obtained
using this BJT? (MAY 12)
10. For an amplifier, mid band gain is 100 & lower cutoff frequency is 20KHz. Find the gain of
an amplifier at frequency 20Hz.
11. For an amplifier, 3dB gain is 200 & higher cutoff frequency is 20KHz. Find the gain of an
amplifier at frequency 100KHz.
12. Why common base amplifier is preferred for high frequency signal when compared to CE
amplifier?
13. What is the difference between small signal equivalent & hybrid π equivalent circuit.
14. What is high frequency effect?
15. What are the causes for occurrence of upper cutoff frequency in BJT?
16. What is Miller’s effect? What is gain bandwidth product?
17. What is Millers effect on Frequency response of an Amplifier.( Nov 14)
18. Relate gain and bandwidth of single and multistage amplifiers. ( Nov 14)
19. What is significance of octaves and decades in frequency response?
20. What are the causes for occurrence of upper cutoff frequency in BJT?
21. What is the major contribution to the Miller capacitance in a MOSFET?
22. What is significance of gain bandwidth product? [DEC 11,May-2008]
23.Define Bandwidth [NOV/DEC-09,11]
24.Define lower and upper cut-off frequencies of an amplifier. [Dec-2005]
25. .Write the overall lower cut-off frequency of multistage amplifier. [May-2008]
27.Write the overall higher cut-off frequency of multistage amplifier.[May-2008]
28. AU-MAY 15
29. Find gain bandwidth product of MOSFET with gm=6mA/V cgs=8Pf, cgd=4 pF ,
cds=1pF [ MAY-15]
30. For an amplifier,midband gain=100 and lower cutoff frequency is 1 KHz. Find the gain of
an amplifier at frequency=20 Hz.
PART-B
1. Using hybrid π model, draw the high frequency equivalent circuit of CE amplifier and derive
high cutoff frequency.(DEC-10)
2. Derive gm for C-E hybrid model.
3. Derive the expression for the CE short circuit current gain of transistor at high frequency.
4. What is the effect of Cµ on the input circuit of a BJT amplifier at High frequencies?
5. Discuss the low frequency response & the high frequency response of a CE amplifier. Derive
its cutoff frequencies.
6. AU- MAY 15
7. Discuss the low frequency response & the high frequency response of a CS amplifier. Derive
its cutoff frequencies. (NOV 14)
8. With neat sketch explain hybrid π CE transistor model. Derive the expression for various
components in terms of ‘h’ parameters.
9. Discuss the frequency response of multistage amplifiers. Calculate the overall upper & lower
cutoff frequencies. (MAY 12).
10.Derive fα, fβ and fγ. (Nov 14)
11.NOV 14
12. 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.
13.
14.
15.
16.
17.
18.
19. A three stage RC coupled amplifier uses identical stages with cutoff frequencies F1=100 Hz,
F2=500 KHz. Find the overall cutoff frequency values.
20. Discuss the frequency response characteristics of RC coupled amplifiers. Derive general
expression for gain at low, middle and high frequencies.[Dec 12]
Unit V-IC MOSFET Amplifiers
PART -A
1. State the advantages of current steering.
2. Define current steering.
3. Compare NMOS with enhancement, depletion and resistive load [May ’15]
4. List out the advantages of CMOS Differential amplifier over
MOS Differential amplifier. (May ’15)
5. Define common mode rejection ratio?
6. Draw the current source using MOSFET. ( NOV’14)
7. Draw CMOS amplifier NMOS as driver and PMOS as load. ( NOV’14)
8. Sketch the DC transfer characteristics of a MOSFET differential amplifier.
9. Draw the current source using MOSFET with active load.
10. What are the advantages of an active load?
11. State the limitation of NMOS amplifier with enhancement load.
12. What is the impedance seen looking into a simple active load?
13. How the reference portion of the circuit can be designed with MOSFETs only?
14. How should a MOSFET be biased so as to operate as a stable current source?
15. Draw the circuit of MOSFET differential amplifier with active load.
16. What is the need for MOSFET differential amplifier with cascode active load?
17. Draw the circuit of CMOS differential amplifier.
18. What is meant by matched transistors?
19. Define common mode and differential mode.
20. What are the limiting factors for the maximum current in MOSFET?
21. Define enhancement and depletion mode of MOSFET.
22. Define saturation and non- saturation bias regions.
23. How do you prove that a MOSFET is biased in the saturation region?
24. Draw MOSFET cascode current source circuit.
25. State the advantage of Wilson current mirror.
26. List the various types of active loads.
27. What is Widlar current source
28. What is cascode current mirror?
29. Give the expression for gain and output impedance for NMOS common source amplifier.
30. Define override voltage.
PART –B
1. Describe the operation of an NMOS amplifier with either an enhancement load, a depletion
load, or a PMOS load.
2. Draw current steering circuit with two source and two sink terminals. Derive the expression
of terminal current in terms of reference current. ( NOV’14)
3. Derive gain, input and output impedance of common source amplifier with NMOS diode
connected active load. ( NOV’14)
4. Explain the basic MOSFET current circuits and discuss its operation.
5. Draw the MOSFET cascode current source circuit, explain and discuss the advantage of this
design.
6. Sketch and describe the advantages of a MOSFET cascode current source used with a
MOSFET differential amplifier.
7. Design a CMOS differential amplifier with an output gain stage to meet a set of
specifications. The magnitude of voltage gain of each stage is to be at least 600. Bias
currents are to be IQ=IREF=100µA,and biasing of the circuit is to be v+=2.5 v and v- =2.5 v.
8. Explain CMOS differential amplifier and derive CMRR.
9. Draw a Widlar and Wilson current source and explain the operation.
10. Describe the operation of a PMOS amplifier with an enhancement load and a depletion load.
11. Explain the CMOS common source and source follower with neat diagram.
12. Explain the large signal behavior of MOSFETs and compare the operating regions of
Bipolar and MOS transistors.
13. Discuss the operation of NMOS amplifier with depletion load and derive its small signal
voltage gain.
14 . Design a MOSFET current source amplifier for following specifications
VDD=5 V,Kn=40µA/V 2 ,VT=1V, λ=0, IREF=0.2 mA, I0=0.1mA and VDS2(sat)=0.8V.
15. Derive the expression for gain and output impedance of NMOS source follower amplifier.
16.Calculate the small signal voltage gain for a CMOS common source amplifier kn=80µA/V 2
kp=20µA/V 2 ,VTn=0.8V, VTp=-1V, λ1= λ2 =0.01, Ibias=0.2 mA, Io=0.1mA , (W/L)n=10
and (W/L)p = 20.
17.Calculate the small signal voltage gain ,gm, ro1 and ro2 for a CMOS common source
amplifier kn=387µA/V 2 kp=86µA/V 2 ,VTn=0.8V, VTp=-1V, λ1= λ2 =0.01, Iref=100µA,
|VAp| =6v/ µm and (W/L) =7.2 µm/0.36 µm .
AU- MAY 15
19.An active loaded MOS differential amplifier (W/L)n=100 (W/L)p=200
µncox=2µpcox=0.2mA/V 2 ,Van=VAp=20v,I=0.8 mA,Rss=25KΩ. Calculate Gm, Ro, Ad,
|Acm| and CMRR.
20.For a Current steering circuit circuit VDD=VSS=1.5V,Vtn=0.6 V,Vtp=-0.6 V ,channel
length=1µm, kn=200µA/V 2 kp=80µA/V 2 , λ =0, Iref=10µA. Find the widths of all
transistor to obtain I2=60µA, I3=20 µA and I5= 80 µA.
21. Find R for a MOSFET current source with following specifications
VDD= 3v , Vt=0.7v , kn=200µA/V 2 , kp=80µA/V 2 , channel length=1µm and Iref=100µA .
22. Describe the operation of a NMOS amplifier with an enhancement load and a depletion
load.
23. [May ‘15]