BPUT QUESTION BANK FOR 4th SEM EC1, EC2 & EE STUDENTS (SESSION -2009-10)

BPUT QUESTION BANK FOR 3rd SEM CS STUDENTS (SESSION -2011-12)

SUB- PSD

MODULE -1 [SHORT QUESTIONS]

1. The effective density of states function Nc at a given temperature for gallium arsenide is much less than the corresponding value for silicon & germanium. Identify the probable reason.

2. Which of the following material has highest electron mobility at a given temperature & low doping concentration silicon, GaAs or Germanium ?

3. Under low-level injection condition , give a relation for recombination rate of excess minority carriers in a p-type semiconductor.

4. Distinguish between the two processes of current flow- drift & diffusion.

5. What is phonon scattering ? How does it affect the carrier mobility in a semiconductor? What is the effect of temperature on carrier mobility ?

6. How do the Intrinsic Fermi levels change, if the effective masses

7. of electrons & holes are unequal ?

8. Draw the energy band diagram for a degenerate semiconductor. Under what condition , a semiconductor becomes degenerate ?

9. Is it possible to have an energy level in the forbidden gap ? Discuss.

10. Interprete the equation Nopo=ni2 ,the terms carry their usual meaning.

11. Write down the expressions for the distribution of charge carriers in the respective energy bands in terms of Fermi-Dirac probability function & the density of quantum states for a semiconductor.

12. Define Fermi level. Indicate its positions for an intrinsic semiconductor at T =0K & at T > 0K.Show graphically how the Fermi level in an extrinsic semiconductor depends on degree of doping .

13. An n-type semiconductor is doped at Nd =1016 cm-3. Assume 1014 electron-hole pairs per cm3 have been created at t=0. Determine the minority carrier concentration at t= 5 ns.

14. 13.Draw a plot to depict the density of states function in the conduction & valency band & the Fermi-Dirac probability function for T > 0K for an intrinsic semiconductor.

15. Write the expression for total drift current density in a semiconductor. Label the terms used.

16. When do the holes &electrons drift or diffuse together in a semiconductor with a single effective mobility on diffusion coefficient?

17. The position of Fermi-energy level in a semiconductor is located in

18. Conduction band,(ii)Valence band ,(iii)Forbidden energy gap

19. Justify your answer.

20. What do you mean by a hole & its effective mass in a semiconductor ?

21. What is Einstein relationship ? What about its significance ?

22. Comment & explain about the temperature coefficient of resistance of a semiconductor ?

23. What do you mean by mobility of charge carriers ? How conductivity & mobility are related to each others ?

24. Explain how you can generate excess carriers in a semiconductor which is under thermal equilibrium ? Derive the minority carrier concentration equation .

25. What is mean lifetime of minority carriers ?

26. An electron with an energy of 2 eV impinges on a potential barrier with Vo =10 e V & width of 2 .Calculate the probability of the electron tunneling through the barrier.

27. What is freeze out condition for an extrinsic semiconductor ? Where is the location of Fermi level in this case ?

28. What is meant by compensated semiconductor ?When does a compensated semiconductor shows the characteristic of an intrinsic material?

29. Draw the energy band structure diagram of:

30. (i)a direct band gap

31. (ii)an indirect band gap semiconductor.

32. Indicate the significance of difference between them.

33. What is meant by ambipolar transport in a semiconductor ?

34. Explain density of states function. 35. What is effective mass?36. What is Fermi energy? Discuss the variation of Fermi energy with temperature using suitable expression & plot.

37. Calculate the drift current density in a sample of silicon at T=300K with doping conc. Nd =1015 cm-3 & Na=1014 cm-3,if the applied electric field is E= 35V/cm,mobility of electrons & holes are 1350 cm2/v.s respectively.

38. What do you mean by intrinsic carrier concentration (ni)? How is it related with noand po ?

39. What is freeze out condition?40. Determine the total number at energy states in Ga As between Ec and Ec + RT at T = 300K.41. Interpret the equation NO PO ni 2. The terms carry their usual meaning.42. What do you mean by a hole and its effective mass in a semiconductor?LONG QUESTIONS

1. A bar of n-type silicon with a cross-sectional area of 1 mm2 & a length of 1 cm is connected to a 2v battery supply & is carrying a current of 2mA at 300K.

a. Calculate the thermal equilibrium electron & hole densities in the bar.

2. b)Calculate the dopant concentration presuming that only doors with an energy level of 0.148 eV below the conduction band are present.

3. c)Determine the temperature at which the bar becomes intrinsic.

4. ni =1.5 x 1016 /m3 ,NC for Si =2.8 x1019 /cm3, bn =1350cm2/Vs

5. How does the position of the Fermi energy level change as a function of the doping concentration & as a function of temperature ? Discuss.

6. For Silicon at T=300K containing an acceptor impurity concentration of Na =1016cm-3(The Fermi energy level is 0.20 eV below the conduction band edge). Calculate the concentration of donor impurity atoms that must be added to make the Silicon n-type.

7. Define mobility & diffusion co-efficients for charge carriers in a semiconductor .

8. Derive the Einstein relation linking mobility & diffusion co-efficient.

9. Calculate the diffusion current density of an n-type semiconductor (T=300K),when the electron diffusion co-efficient Dn =225cm2/s. Assume the electron concentration varies linearly from 1x1018 to 7x 1017 cm-3 over a distance of 0.1 cm.

10. Draw the plot for the density of state functions in the conduction band, valence band & the Fermi-Dirac probability function at T > 0K for an intrinsic semiconductor. Indicate the areas representing electron & hole concentration. How does this plot get modified for an extrinsic semiconductor ? Explain with diagram for both P & N type.

11. Calculate the drift current density in GaAs at T=300K if the applied electric field E=5V/cm with doping concentration Na=0 & Nd =1016 cm-3. Given ni=1.8x106 cm-3, n =8500cm2/v-s & =400cm2/v-s at T=300K. Assume complete ionization.

12. What do you mean by intrinsic carrier concentration in semiconductor? Explain with mathematical expression how the charge densities change when dopants are added ?

13. What do you mean by the statement: An electron & hole recombine & disappear?

14. Derive the ambipolar transport equation.

15. Derive the expression for the thermal equilibrium concentration of holes in the valence band using effective density of states ,Fermi energy, Fermi function & other terms.

16. Calculate the thermal equilibrium hole concentration in silicon at T=400K.Assume that the Fermi energy is 0.27 eV above the valence band energy.The value of NV for silicon at T =300K is NV =1.04 x 1019 cm-3.17. Derive the expression for thermal equilibrium concentration of holes in the valence band using effective density of states function, Fermi energy and other terms.

18. Calculate the thermal equilibrium hole concentration in silicon at T = 400 K. The Fermi energy is 0.27 eV above the valence band energy. Nv = 1.04 x 1019 cm-3 at T = 300K.

19. Explain the variation of Fermi energy level with doping ****** and temperature

using suitable expression and plot.

20. The Fermi energy level for a particular material at T = 300K is 6.25 eV. Find the probability of an energy level at 6.50 eV, being occupied by an electron.

MODULE -2 [ SHORT QUESTIONS]

21. Draw & label the energy band diagram of a pn junction in thermal equilibrium.

22. Sketch the steady state minority carrier concentration in a forward biased pn junction.

23. What is meant by Base width modulation ?

24. What is meant by storage time for a BJT ?Explain its role in limiting the speed of a switching transistor.

25. Represent graphically the electric potential through the space charge region of a uniformly doped pn junction.

26. Consider a silicon pn junction at T=300K with doping concentration of Nd=1015 cm-3 & Na =1016 cm-3 .Given Vbi =0.635V& s =11.7x8.85x10-14 F/cm. Calculate the space-charge width in the pn junction.

27. Calculate the diffusion resistance of a PN junction diode for a quiescent current of 2mA .

28. Distinguish between zener & avalanche mechanism of breakdown in a reverse biased PN junction diode.

29. What is meant by Early effect ? Draw IcVs VCE plot for a BJT showing the Early effect & Early voltage.

30. When does breakdown occurs in a bipolar transistor due to punch-througheffect ? Name the physical parameters of a BJT that determines the punch-through voltage.

31. High frequency transistors must have small diffusion capacitance. Why ?

32. Calculate the collector-emitter saturation voltage of a bipolar transistor at T=300K. Given F =0.99 ,R=0.20,IC=1mA & IB=50 A .

33. Write the expression for carrier diffusion co-efficient in a semiconductor. State its sign & unit . What is the significance of diffusion co-efficient ?

34. What is implied by Low injection for an extrinsic semiconductor ? Show that the ambipolar diffusion co-efficient & ambipolar mobility values reduces to minority carrier values under this condition.

35. Draw the plot for electric field & Electric potential in the space charge region of a uniformly doped PN junction. What are the significant differences in the features of these curves ?

36. What is meant by diffusion resistant of a PN junction diode ? Explain how it is assessed from the V-I characteristics of the diode.

37. Explain Early effect in a BJT. How is Early voltage determined using the IC versus VCE plot ?

38. Discuss the factor limiting the switching speed of a transistor.

39. With the help of suitable diagrams, explain the minority carrier distribution in an npn bipolar transistor operating in

40. Cut-off (ii) Saturation mode .

41. In a silicon bipolar transistor, =100 & the base doping concentration NB =1017 cm-3. What should be the minimum open-emitter junction breakdown voltage if the minimum open-base breakdown voltage is 15 volts ?

42. Can you measure the in-built potential difference across the junction of a PN junction diode using a voltmeter ? Explain your answer.

43. The spread of depletion region is more to the p-side of a junction diode. Comment on the doping levels.

44. What is meant by diffusion capacitance of a p-n junction diode ? Whose magnitude is more diffusion capacitance in a forward biased p-n junction or the junction capacitance ?

45. What is meant by reverse saturation current in a pn junction diode? How the V-I characteristics change with temperature ?

46. Which of the bipolar transistor configuration has the highest Ri &low Ro? Justify with proper equations.

47. Is |VBE,sat| greater /less than |VCE,sat| ? Explain.

48. Explain the terms :diffusion length, diffusion constant & mean lifetime of charge carriers in a semiconductor. State any relationship that exists between them.

49. What do you mean by minority carrier storage time of a diode ?

50. 29.What do you mean by diode breakdown ?Explain the mechanisms involved for such behavior.

51. Write the Eber-Moll equations for a BJT . Sketch the circuit model which satisfies these equations.

52. What is meant by inverted model of operation of a BJT ?

53. Assuming 1014 electron-hole pairs per cm3 have been created at t=0 in n-GaAs doped at Nd =1016 cm-3 & minority carrier hole lifetime po =10ns, calculate the time during which the excess hole & excess electron concentration will decay to 1/e of their initial values.

54. The peak electric field in a space charge region of a pn junction is quite large, yet there is no drift current. Why ?How is the spread of depletion region into the doped regions dependent on the doping level in them ?

55. Name the factors that governs the junction capacitance of a reverse-biased junction diode .

56. Draw the bipolar transistor CE current-voltage characteristic with load line superimposed on it .Indicate the region for which the relation IC= IB is valid.

57. Explain the current crowding effect in a bipolar device.

58. Define the emitter injection efficiency factor for a bipolar transistor. Explain why the emitter doping should be large compared to the base doping.

59. Assuming carrier mobility of 1000 cm2 /V.s at T=300 K , determine the diffusion coefficient.

60. Show that for an extrinsic p-type semiconductor under low injection, the ambipolar diffusion coefficient & the ambipolar mobility coefficient reduce to the minority carrier electron parameter values.

61. How is an electric field created in the depletion region of a junction diode? Draw a diagram to show the space charge density in a uniformly doped pn junction assuming the abrupt junction approximation.

62. In a silicon pn-junction ni=1.5x1010 cm-3 at T=300K. Assuming n-type doping of 1x1016 cm-3 at a forward bias of 0.6 V applied to the p-n junction, calculate the hole concentration at the edge of the space charge region.

63. Starting from the ideal diode equation , derive an expression for the diffusion resistance of a junction diode.

64. Draw the energy band diagram of an n-p-n bipolar transistor-

65. under zero bias & (ii)under a forward-active mode bias

66. What are the different operating modes of a bipolar transistor ? Using VBE versus VCB plot, indicate the junction voltage condition of these modes.

67. Show graphically the minority carrier distribution in an n-p-n transistor operating in the forward active mode.

68. The emitter & base of a silicon n-p-n bipolar transistor are uniformly doped at impurity concentrations of 1018 cm-3 & 1016 cm-3 respectively. The neutral base width is B =2m, the minority carrier diffusion length in the base is LB=10 B & the applied forward-bias B-E voltage, VBE=0.61 V.

69. Calculate the excess minority carrier concentration in the base at

70. (i)x=0, (ii) x= B/2

71. What is avalanche breakdown ?

72. What is meant by base width modulation ?

73. Why the base region of a transistor is made very thin ?

74. Define &derive the expression of built-in potential barrier voltage for a pn junction in thermal equilibrium.

75. Calculate the built-in potential barrier in a silicon pn junction at T=300K for Nd =1016 cm-3 & Na=5x1017 cm-3 .Assume that ni=1.5x1010 cm-3.

76. Discuss the punch-through breakdown in BJT. Write the expression for the punch through voltage.

77. Write the Ebers-Moll equations for a BJT. Sketch the equivalent circuit which satisfy these equations.78. Calculate the built-in potential barrier for silicon pn junction at T = 300 K for Na = 5 x 1017 cm -3, Nd = 1016 cm-3.79. What is punch-through breakdown in BJT?80. What do you mean by generator and recombination rates?81. Write the expressions for carrier diffusion co-efficient in a semiconductor. State its sign and unit.82. What do you mean by drift and diffusion densities in semiconductor? Write the expressions for them.

83. Derive the expression of the excess minority carrier electron concentration in the forward active mode in an n pn bipolar transistor.

84. What is base width modulation? Explain with suitable diagram.

85. What are the different modes of operation of a BJT? In which mode maximum current flows and why?

86. With the help of suitable diagram, explain the minority carrier distribution in an npn bipolar transistor operating in saturation mode.87. Explain Early effect in BJT. How Early voltage is determined using the Ic versus VCE plot.88. What is meant by diffusion resistance of a PN junction diode? Explain how it is assessed from the V-I Characteristic of the diode.89. Why BJT is a bipolar device, whereas MOSFET is a unipolar device?90. Is |VBE.sat| greater or less than |VCE.sat|? Explain.91. Which of the bipolar transistor configuration has the highest input resistance Ri and the lowest output resistance Ro? Justify with proper equations.92. What is meant by inverted mode of operation of a BJT?93. Plot minority carrier concentration as a function of distance form the p-n junction under different bias conditions, indicate the excess concentration in the diagram. What is the law of junction?

LONG QUESTIONS

94. Derive the time-dependent diffusion equations for excess carriers in a semiconductor. Modify the equations to contain terms involving the total concentration & the excess concentrations.

95. Deduce the Einstein relation for a uniformly doped semiconductor in thermal equilibrium. Is the diffusion co-efficient for a carrier of the same order as its mobility ? Determine the diffusion co-efficient given the carrier mobility 100 cm2/V.s at T=300K.

96. Derive an expression for space charge width in a pn junction.

97. Discuss the frequency limitations of BJT as a circuit device .Calculate the emitter to-collector transit time & cut-off frequency of a bipolar transistor at T=300K. Assume the following parameters.

98. IE =1 mA, Cje =1Pf, XB=0.5m, Dn=25 cm2 /s, Xdc =2.4 m, rc =20, C =0.1Pf, Cs =0.1Pf

99. Neglect the parasitic capacitance.

100. (a)Show graphically the minority carrier distribution in an npn bipolar transistor operating in forward- active mode .Explain the notations used.

101. (b) Compare the distribution given in (a) with distribution given in bipolar transistor operating in (i) cut off (ii)saturation and (iii) inverse-active mode.

102. Derive the ideal current-voltage relationship of a PN junction diode.

103. Given pn junction(T=300K) have ni =1.5x1010 cm-3 & the n-type doping is 1016cm-3 .Calculate the minority carrier hole concentration at the edge of the space charge region , when a forward bias of 0.6 V is applied to the pn junction.104. Consider an NPN bipolar transistor biased in the active mode .Using Ebers-Moll model, derive the equation for the base current ,IB,in terms of F, R, IES,ICS & VBE.

105. Which factors cause time delay in a bipolar transistor ? Discuss.

106. Describe the large signal switching characteristics of a bipolar device.

107. Draw the plot to indicate the carrier drift velocity saturation in a semiconductor with applied electric field. Explain the features of the plot. Which feature in this plot differentiates GaAs from Si/Ge ?

108. Derive the time-dependent Diffusion equations for holes & electrons in a semiconductor .How are the equations modified for a homogeneous semiconductor ?

109. Derive an expression for the built-in potential barrier at a PN junction. Why cant this potential be measured by a voltmeter ?

110. Calculate the built-in potential barrier in a silicon PN junction at T=300K for, (i)Na=5x1017 cm-3 ,Nd =1016cm-3

111. (ii) Na=1015 cm-3 ,Nd =2x1016cm-3 . Assume ni =1.5 x 1010 cm-3

112. What do you infer from these results ?

113. Derive the ideal diode equation for a PN junction diode . Under what condition does the reverse-bias current density becomes independent of the reverse-bias voltage.

114. Consider a silicon PN junction diode at T=300K with an applied format bias voltage Va =0.65 V, Given, Nd=1016cm-3, n=1350cm2 /v-s & the reverse saturation current JS =4.15x10-11 A/cm2. What is the total current far from the junction in the n-region ? What is the electric field across the junction ?

115. Explain the different breakdown mechanisms in a BJT. Derive necessary expressions to calculate breakdown voltage in each case.

116. Develop the basic Ebers-Moll equivalent circuit of a bipolar transistor. Derive necessary expressions.

117. 18.Using the Ebers-Moll equations, calculate the collector-emitter saturation voltage of a bipolar transistor at T=300K.

118. Assume, F =0.99,R =0.20,IC =1mA,IB=50 A & Vt =0.0259 .

119. Plot the minority carrier concentration as a function of distance from the p-n junction under different bias conditions. Indicate the excess concentration in the diagram. What is the law of junction ?

120. Sketch the output characteristic plot for a p-n-p CE transistor configuration. Indicate the active ,saturation & cutoff region in the above plot. Derive the expression for IC versus IB for the active region of transistor operation.

121. Give the h-parameter model for the common base transistor configuration. Derive the expression AI & Ri in terms of h-parameters & the load impedance.

122. Draw the small-signal high-frequency CE model of a transistor. What is the physical origin of the capacitors in the model ?

123. Derive the Einstein relation linking the diffusion co-efficient & charge mobility.

124. Analyzing the electric field in the depletion region show that the number of negative charges per unit area in the p-region is equal to the number of positive charges per unit area in the n-region.

125. With necessary diagram, explain the complete small-signal equivalent circuit of forward-biased p-n junction diode.

126. Given,T=300K,po=10-7 s, IPO-IDQ=1m A , & Na >>Nd127. Develop the basic Ebers-Moll equivalent circuit of a bipolar transistor. Write the expressions for collector & emitter currents.

128. Write the expression for drift & diffusion current densities. Derive Einstein relation showing relationship between diffusion constant Dn & mobility.

129. Derive the ideal diode equation for a pn junction .Under what condition does the reverse bias current density becomes independent of the reverse bias voltage. Plot the I-V characteristic curve.

130. Derive the expression for the excess minority carrier electron concentration in the forward active mode in an npn bipolar transistor.

131. Derive the expression for the electric field in the space charge region of the uniformly doped pn junction, where does the maximum electric field occur in the space charge region.

132. Determine the ideal reverse saturation current density in a silicon pn junction at T =300K, considering the following parameters in a silicon pn junction,

133. Na=Nd =1016cm-3,ni=1.5x1010 cm-3,Dn=25 cm2/s,Dp=10cm2/s,po= no=5x10-7s,r =11.7134. Derive Einstein relation. State the changes occurring in these relations for a n type and p type semiconductor.

135. Determine the diffusion coefficient. Assuming the mobility of a particular carrier is 1000 cm2/v-s at T = 300K.

136. Derive expression for the electric field and potential in the space charge region of a uniformity doped pn junction. Derive expression for the space charge width of the junction.

137. A silicon pn junction at T = 300K with zero applied bias has doping concentration of Na = 5 x 1015 cm -3. Determine the space charge width.

138. A silicon pn junction at T = 300K. Intrinsic carrier concentration Ni = 1.5 x 1010 cm-3. The n type doping concentration is 1 x 1016 cm-3, and a forward bias if 0.60V is applied to the pn junction. Calculate the minority carrier hole concentration at the edge of the space charge region.

139. Derive the ideal diode equation for a pn junction and draw the I-V characteristics curve, under what condition does the reverse bias current density becomes independent of the reverse-bias voltage.

140. What do you mean by diode breakdown? Explain the mechanism involved for such behavior?141. Derive the ideal diode equation for a p-n junction diode. Under what condition does the reverse-bias current density becomes independent of the reverse-bias voltage?142. Discuss Ebers-Moll Model and calculate VCE (sat) of a BJT at T = 300 K, provided F = 0.99, R = 0.20, Ic = 1mA and IB = 50 A.143. Draw the small signal equivalent circuit of a BJT and determine the approximate frequency at which the small signal current gain decreases to 1/2 of its low frequency value, provided if input resistance and capacitance values are 2.5 K and 4.0 F respectively then calculate the frequency.

144. Draw the output characteristic plot for a p-n-p CE transistor configuration. Indicate the active, saturation and cutoff regions in the above plot. Derive the expression for Ic versus IB for the active region of the transistor operation.145. An n-type semiconductor is doped at NA = 1016 cm-3. Assume 1014 electron-hole pairs per cm3 have been created at t = 0. Determine the minority carrier concentration at t = 5 ns.146. Give the h-parameter model for the common base transistor configuration. Derive the expression for current gain Ai and input resistance Ri in terms of h-parameters and the load impedance.

147. Draw the small signal high frequency common emitter model of a bipolar junction transistor. What is the physical origin of the capacitor in the model?

148. Derive Einsteins relation between carrier mobility and diffusion co-efficient in a semiconductor.149. Consider a GaAs PN junction with doping densities of NA = 1018 cm-3and ND= 1015 cm-3 . Calculate the built in potential barrier in this junction.

a. If the acceptor doping concentration changes from NA= 1018 cm-3 to NA=1016 cm-3, then find the changes in potential.

MODULE -3

SHORT QUESTIONS

1. Define Flat-Band voltage for a MOS capacitor . Which are the parameters that determine its value ?

2. What is meant by latch-up in a CMOS circuit ? How can it be prevented ?

3. In an n-channel JFET, internal pinch off voltage is 4.35 V & the built-in potential barrier is 0.814 V .Calculate the pinch-off voltage.

4. Define flat-band voltage .Draw & explain the energy band diagram of a MOS capacitor at flat band.

5. What are the basic frequency limitation factors in the MOSFET ? Which of them is important ? why ?

6. For an Al-SiO2 junction ,in a MOS system , the modified work function m1 =3.20 V & for silicon-silicon dioxide junction, the modified electron affinity 1 =3.25 V. Given , at T=300K, P-type doping concentration Na =1014 cm-3, Eg =1.11ev,ni =1.5x 1010 cm-3. Calculate ms .What happens if Na is changed to 1016 cm-3 ?

7. Why BJT is a bipolar device, whereas MOSFET is a unipolar device?

8. What are advantages of CMOS logic circuit over other MOS circuits?

9. Draw the energy-band diagram through the MOS structure with an n-type substrate for a negative applied gate voltage.

10. In which way n-type MOSFET is different from p-type MOSFET ?

11. What is pinch off voltage ?

12. Draw the energy band diagram for a metal semiconductor junction under forward & reverse bias .

13. What are the basic differences between MOSFETS & JFETS ?

14. What are the differences between a Schottky barrier diode & pn junction diode.

15. Describe what is meant by inversion layer of charge. Describe how an inversion layer of charge can be formed in a MOS capacitor with a p-type substrate.

16. Assuming a barrier height of 0.67V,calculate the effective Richardson constant from the I-V characteristic at T=300K given that Jst=8x10-5A/cm2.

17. Calculate the flat band voltage for an MOS capacitor with a p-type semiconductor substrate doped to Na=1016cm-3,a silicon dioxide insulator with a thickness of tox=200,an n+ polysilicon gate & an oxide charge of Q1ss=8x1010cm-2.

18. What are the differences between schottky barrier diode and pn junction diode? 19. What are the basic differences between JFET and MOSFET?20. Define inversion layer of charge and when it is formed?21. What is flat bond condition in a MOS device? Write expression for flat band voltage.

22. What are the advantages of CMOS Logic circuit over other MOS circuits?LONG QUESTIONS1. Describe the structure & working of a MOS capacitor . Give the necessary energy band diagram.

2. Give the basic structure of an MOS capacitor .Draw & compare the energy band diagrams of a MOS capacitor with a p-type substrate using (i)negative gate bias (ii) moderately positive gate bias & (iii) a large positive gate bias.

3. A MOS structure with p-type semiconductor substrate doped to Na=1016 cm-3 has a silicon dioxide insulator with a thickness of tox=500 & an n+Polysilicon gate. Assuming Q1ss=1011 electronic charges/cm2. Calculate the flat band voltage for the device.4. Draw the energy band diagram through the MOS structure in thermal equilibrium after contact. Derive an expression for metal-semiconductor work function difference.

5. Draw the basic construction of a p-channel depletion type MOSFET. In what ways the construction of a depletion-type MOSFET similar & different to that of a JFET ?

6. What is the significant difference between the construction of an enhancement type & a depletion type MOSFET ?

7. Describe the basic operation of an enhancement-type MOSFET. Sketch the transfer & drain characteristics of a typical n-channel enhancement-type MOSFET.

8. What do you mean by a CMOS logic design ?Construct the basic CMOS inverter from the basic MOS devices & explain its operations. Suitably modify the circuit to implement a NAND and a NOR gate.

9. With a neat sketch , describe the basic structure of an n-channel enhancement mode MOSFET.

10. Draw the ID versus VDS characteristics of the above MOSFET for different values of VGS. Explain the features of the curves.

11. Derive an expression for flat band voltage & threshold voltage for a MOS device.

12. 12.What do mean by CMOS technology? Sketch the cross section of a CMOS structure. Discuss what is meant by latch up in a CMOS structure. What do you mean by CMOS technology? Sketch the cross section of a CMOS structure. Discuss that is meant by latch-up in a CMOS structure.

13. Calculate the flat-band voltage e for a MOS capacitor with a p-type semiconductor substrate doped to Na = 1016 cm-3 ,a SiO2 insulator with a thickness of tox = 500 and an n+ polysilicon gate, assuming that Qss = 1011 electronic charge/cm2.

14. Draw the energy band diagram through the MOS structure in thermal equilibrium after contact. Derive an expression for metal-semiconductor work function difference.

15. Construct the basic CMOS inverter from the basic MOS devices and explain its operations. Suitable modify the circuit to implement a NAND and a NOR gate.

16. What are the significant differences between the construction of an enhancement type and depletion type MOSFET?