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2007 SRM University B.Tech Electronics and Communications Engineering QUESTION BANK ELECTRONIC DEVICES Question paper



Course: B.Tech Electronics and Communications Engineering   University/board: SRM University


















SRM INSTITUTE OF SCIENCE AND TECHNOLOGY
(DEEMED UNIVERSITY)

QUESTION BANK

I YEAR B.Tech (II Semester)

ELECTRONIC DEVICES

(COMMON FOR EC102, EE104, IC108, BM106)














UNIT-I


PART-A


1. What are intrinsic and extrinsic semiconductors?
2. List the properties of semiconductors.
3. Draw the energy band diagram of germanium and a metal.
4. What do you mean by Valance electron?
5. How drift current is produced?
6. Define ‘electron volt’.
7. The relationship between field intensity and potential is given by ______________.
8. Draw the path of an electron in perpendicular electric and magnetic fields when the initial velocity is zero.
9. Write the equation for the period and angular velocity of a particle in a magnetic field.
10. What is the value of Eg for Ge and Si at room temperature (300k)?
11. Draw the energy band diagram of a semiconductor and conductor.
12. Draw the motion of a charged particle in a magnetic field.
13. What is drift current? Upon what factors it depends?
14. Why do we go for Extrinsic semiconductor?
15. How is extrinsic semiconductor formed?
16. List the pentavalent and trivalent impurities.
17. Draw the motion of a charged particle in a uniform electric field.
18. What is diffusion current?
19. Distinguish between Drift and Diffusion current.
20. The e/m value of electron is _____________.
21. Differentiate insulators, semiconductors and metals.
22. Explain what is hole. How do they move in intrinsic semiconductor?
23. What does doping in semiconductor mean?
24. Explain majority and minority carrier in semiconductor?
25. What is fermi level? How is it useful in the analysis of semiconductors?
26. Define the term’s conductivity and mobility in semiconductor.
27. State Einstein relationship.
28. Define carrier lifetime.
29. State mass action law.
30. Write down the expressions, which are used for finding the electron and hole concentration.







PART-B

1. Explain motion of an electron in electric field.
2. Explain motion of an electron in magnetic field.
3. Discuss motion of an electron in both magnetic and electric field.
4. Derive the continuity equation from the first principle.
5. Derive the Fermi – level equation for an intrinsic semiconductor with the Energy band diagram.
6. Explain drift and diffusion current and write the expressions for total Current density due to holes and electrons
7. Explain mass action law.
8. Derive the equation for the concentration for holes and electrons.
9. Explain in detail the classification of solids with energy band diagram.
10.Explain about:
a) Donor atoms
b) Acceptor atoms
c) Intrinsic semiconductors
d) N-type Extrinsic Semiconductor
e) P-type semiconductor
11. Explain about:
a) Valence shell
b) Valence electron
c) Free electrons
d) Holes
e) Covalent bond with suitable diagram























UNIT-II

PART-A



1. What is meant by photoconductivity?
2. Explain cutin voltage of a diode.
3. What is Zener breakdown?
4. Give some applications of varactor diode and its symbol.
5. Sketch the VI characteristics of a tunnel diode.
6. State the relative merits of pin photodiodes and avalanche photodiodes.
7. The leakage current of a PN diode is caused by ____________.
8. Define DC (or) Static resistance (RF).
9. Define AC (or) Dynamic resistance (rF).
10. How is depletion region formed?
11. Give the advantages of using LCD over LED.
12. Draw the circuit model for Zener diode.
13. Avalanche breakdown is primarily dependent on the process of ____________.
14. What happens when a p-type material is joined with n-type material?
15. Draw the VI characteristics of LED.
16. The cutin voltages of a Germanium and silicon diodes are ____________.
17. The transition capacitance is also called as __________.
18. Varactor diode is realized with ________ bias given to a junction diode.
19. Define barrier potential.
20. What is “tunneling”?
21. What are the uses of photodiode?
22. State photovoltaic effect.
23. What are the advantages in using cadmium sulphide as semiconductor material in LDR?
24. Draw the symbol for thermistor.
25. The reverse saturation current of silicon PN junction diode is 10?A. Calculate the diode current for the forward bias voltage of 0.6V at 25degree C.
26. What is a PN junction? How it is formed?
27. Explain how a barrier potential is developed at the PN junction.
28. Explain avalanche break down & zener breakdown.
29. Define leakage current. What is the advantage of silicon over germanium?
30. Explain VARACTOR diode and application.
31. Define PHOTODIODE.
32. Advantages and disadvantages of TUNNEL DIODE.
33. What is a PIN diode?
34. Write the Diode Equation how can this be approximated?
35. How is Photodiode different from PhotoVoltaic Cell?










PART-B

1. Draw the energy band diagram of a PN junction and explain the working of diode.
2. Give the diode current equation of PN junction diode.
3. Explain V-I characteristics of PN junction diode.
4. Explain Zener diode with V-I characteristics.
5. Explain TUNNEL diode with neat sketch and VI characteristics.
6. How is a PIN diode different from Semiconductor PN junction diode? Explain its operation with the help of VI characteristics?
7. Compare LED and LCD with sketch.
8. Derive the expression for Minority Carrier Concentration in a PN junction diode.
9. Explain about Varactor Diode.
10. Explain about Avalanche Breakdown and Zener Breakdown.
11. Write short notes on;
a) Photo Voltaic cell
b) Thermistor
c) LDR
12. Explain LED with a neat diagram.


























UNIT –III

PART A

1. What is the need for heat sinks?
2. How should the transistor be biased if it has to be operated in the cut off and saturation region?
3. CE configuration has got _____________ current amplification and _____________ voltage amplification.
4. What are h parameters of CB configuration?
5. Define storage time.
6. Draw the transistor as a switch.
7. Sketch typical common base characteristics of a pnp transistor.
8. Will a transistor result if two diodes are connected back to back?
9. State Early effect.
10. A Common base configuration transistor has a = 0.96 and IE = 2 mA. Find its IC and IB
11. Give the relation between a and ß.
12. Give the h parameters for a transistor circuit.
13. Explain the emitter and base regions of a transistor.
14. Give the relation between emitter, collector and base currents.
15. A common Emitter configuration transistor has ß = 100 and IB = 50µA. Calculate the values of a , IC and IE .
16. A transistor will be in active region when ___________.
17. For power amplification which configuration is generally used.
18. Define rise time.
19. Define delay time.
20. How the transistor is affected by high frequency?
21. Among the 3 configurations (CB, CE, CC) which is having high current gain.
22. The hybrid pi model is also called ___________.
23. The transistor transconductance gm is ___________ proportional to current and _____________ proportional to temperature.
24. Mention some applications of photoconductive cell.
25. A transistor will be in cutoff region when ___________.
26. What are the applications of common collector and common base configurations ?
27. __________ Configuration has high voltage gain, among CE,CC and CB transistors.
28. Why it is called as bipolar junction transistor?
29. What is the difference between PNP and NPN transistor ?
30. What are the different configurations of BJT?
31. Explain different type of current gain (?,?,?)?Show how they are related with each other?
32. Why are power transistor provided with heatsinks?
33. Define early effect or basewidth modulation of transistor.
34. What is known as Heatsink?
35. Mention the three regions of transistor amplifier using the CB output characteristics.
36. Express any two hybrid Pi parameters in terms of small signal low frequency hybrid parameters.
37. Why is CE amplifiers preferred to others?
38. Draw the hybrid Pi equivalent of BJT.
39. Draw all the possible configurations of NPN transistor?
40. Draw all the possible configurations of PNP transistor?





PART-B

1. Explain CE configuration of BJT with i/p and o/p characteristics.
2. Explain CB configuration of BJT with i/p and o/p characteristics.
3. Explain CC configuration of BJT with i/p and o/p characteristics.
4. Explain Eber’s moll model of PNP transistor. How is this useful in getting output characteristics.
5. Briefly explain the commonly available heatsinks.
6. Derive the hybrid-parameters for CB configuration.
7. Derive the hybrid-parameters for CE configuration.
8. Derive the hybrid-parameters for CC configuration.
9. Explain high frequency ? model for BJT?
10. Compare the CB, CC, CE configuration with application.
11. Explain transistor as a switch (delay time, storage time, rise time, fall time).
12. Derive the current components of BJT.


















UNIT – IV

PART-A

1. FET is a ______________ operated device.
2. Define pinch off voltage.
3. Why is FET called a unipolar device?
4. How can a FET be used as a voltage controlled resistor?
5. Why are FETs are more advantageous than BJT?
6. Give the basic principle of VVR.
7. Give the relation between transconductance gm , drain resistance rd and amplification factor µ of a FET.
8. Differentiate between depletion mode and enhancement mode.
9. Input impedance of FET is _________ than that of junction transistor.
10. Draw the cross section of an n-channel VMOS.
11. Difference between MOSFET & VMOS.
12. Draw the symbol for n-channel and p-channel VMOS.
13. VMOS can be described as ____________ MOSFETS.
14. Write the applications for power MOSFET or VMOS.
15. What are the advantages of VMOS?
16. What are the two types of charge transfer devices?
17. What is BBD?
18. What is CCD?
19. What are the applications of BBD?
20. What are the applications of CCD?
21. Draw the construction for BBD & CCD and give the difference.
22. What do you mean by storage and transfer condition in CCD?
23. Draw the symbol of both n-channel & p-channel, depletion and enhancement MOSFET.
24. Why a Field effect Transistor is called so?
25. What are the relative merits of a N-channel and P-channel FET?
26. Explain why BJT is called bipolar device &FET is called unipolar device?
27. Give some application of FET.
28. What is a MOSFET? How many types of MOSFET are there?
29. How the constructional features of MOSFET differs from JFET?
30. Explain some application of MOSFET&JFET.
31. Explain the difference between UJT and BJT.
32. Explain terms peak point voltage, valley point voltage of a UJT.
33. Mention an application of UJT and draw the circuit symbol and mark the terminals.
34. The main operational difference between UJT and FET is __________ .
35. Explain negative resistance from the characteristics of UJT.
36. Useful behaviour of UJT occurs when the emitter is __________ biased.
37. Draw the drain characteristics of Enhancement and Depletion mode of N-channel MOSFET.
38. How does the gate capacitance of MOSFET affect the performance?
39. What region of drain characteristics is used for VVR operation? Why?




PART-B


1. Explain the construction of N channel JFET with VI characteristics.
2. Define and explain the parameters transconductance gm ,drain resistance rd and amplification factor ? of a JFET. Establish the relation between them and also explain the transconductance varying with drain current and gate voltage.
3. Compare JFET with BJT with the necessary diagrams.
4. Explain how FET is used as voltage variable resistor.
5. Explain the construction and operation of three phase charge coupled device with the necessary diagrams.
6. With the suitable diagram and VI characteristics explain working of MOSFETs.
7. Explain the working and VI characteristics of Depletion MOSFET. What are the merits and demerits of this over enhancement MOSFET?
8. Explain the working and VI characteristics of Enhancement MOSFET.
9. Explain the working and VI characteristics of UJT.
10. Explain with the help a circuit diagram the working of a UJT relaxation oscillator.
11. Explain the operation of BBD with suitable diagrams.
12. Explain the working and VI characteristics of power MOSFET or VMOS.
13. How can a MOS transistor be used as a charge transferring device? Explain with the help of neat diagrams.

























UNIT – V


PART – A



1. Draw the layer model of TRIAC and its symbol.
2. Sketch the VI characteristics of a DIAC.
3. Draw the structure and symbol of DIAC.
4. Sketch the VI characteristics of a TRIAC.
5. What is intrinsic stand off ratio?
6. SCR is a __________ layered device.
7. Name the technology used for fabrication of transmitters or ICs.
8. List the basic process used in the silicon planar technology.
9. Explain the word “Epitaxy”.
10. What is the need for SiO2 layer? How thick is this layer?
11. What is ion implantation? Give its advantages.
12. Give the various isolation techniques used in ICs.
13. Give the steps in photolithography process.
14. List the advantages of IC over discrete component circuit.
15. Sketch the cross-section of a CMOS transistor.
16. Discuss the difference between thin films and thick films.
17. List the various methods used for depositing thin films.
18. Discuss cathode sputtering.
19. Describe thick film technology.
20. What is a GTO?
21. What is the thyristor? Mention some of them.
22. Mention some applications of SCR, TRIAC, UJT.
23. Give the difference between SCR>O.
24. Define latching current & holding current of a SCR
25. What are the advantages of TRIAC over SCR?
26. DIAC is bi-directional device explain.
27. Give the difference between thick film and thin film technology.
28. Mention two ways of turning off a SCR.
29. What are the different ways of Vapour deposition?
30. What is the meaning of twin tub process?













PART-B

1. Explain DIAC with VI characteristics.
2. Explain SCR with VI characteristics.
3. Explain TRIAC with VI characteristics. What is the advantage of TRIAC over SCR?
4. Explain two transistor analogy of a SCR and explain its breakdown operation.
5. Explain the operation of a SCR as a rectifier.
6. Explain steps of fabrication of monolithic integrated circuits in detail.
7. Explain the steps of NMOS fabrication
8. Explain the various methods of fabrication used in CMOS.
9. Explain thin film technology with relevant sketches
10. Explain the thick film technology with relevant sketches.
11. Explain the various steps involved in planar process. Draw the relevant sketches.
12. Explain the steps of PMOS fabrication.
13. Explain twin tub fabrication in detail.































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