MCQOPTIONS
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MCQOPTIONS
This section includes 29 Mcqs, each offering curated multiple-choice questions to sharpen your Electronic Devices Circuits knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
For P-type semiconductor, the dopant is |
| A. | Phosphorous |
| B. | Antimony |
| C. | Bismuth |
| D. | Boron |
| Answer» E. | |
| 2. |
N-type semiconductor is obtained by doping silicon with: |
| A. | Phosphorus |
| B. | Aluminum |
| C. | Boron |
| D. | Germanium |
| Answer» B. Aluminum | |
| 3. |
N-type materials are the type of materials formed by adding group _____ elements to the semiconductor crystals. |
| A. | three |
| B. | four |
| C. | two |
| D. | five |
| Answer» E. | |
| 4. |
In terms of energy bands, insulators have: |
| A. | Full conduction band |
| B. | Very small energy gap |
| C. | Full valence band |
| D. | Moderate energy gap |
| Answer» D. Moderate energy gap | |
| 5. |
In a p-type silicon sample, the hole concentration is (1.5 × 1015)/cm3. If the intrinsic carrier concentration is 3.0 × 1010/cm3, the electron concentration would be ______ |
| A. | 0 |
| B. | 6 × 1010/cm3 |
| C. | 6 × 105/cm3 |
| D. | 1.5 × 105/cm3 |
| Answer» D. 1.5 × 105/cm3 | |
| 6. |
For elements having energy gap more than 5 ev, act as: |
| A. | Semiconductors |
| B. | Insulators |
| C. | Superconductors |
| D. | Conductors |
| Answer» C. Superconductors | |
| 7. |
Acceptor impurity concentration of Si at 300 K is 1019 cm-3. Calculate the concentration of donor impurity atoms that must be added so that Si is n-type and the Fermi Energy is 26 meV below the conduction band edge.(Given : Effective density state Nc = 2.7 × 1019 cm-3 and Thermal Voltage (VT) at 300 K is 26 mV) |
| A. | 1.5 × 1019 cm-3 |
| B. | 3 × 1019 cm-3 |
| C. | 1019 cm-3 |
| D. | 2 × 1019 cm-3 |
| Answer» E. | |
| 8. |
Current in an Intrinsic semiconductor is equal to |
| A. | electron current |
| B. | Hole Current |
| C. | Electron current + Hole Current |
| D. | Displacement current |
| Answer» D. Displacement current | |
| 9. |
N(E): Density of statesf(E): Probability that a quantum state with energy E is occupied by an electronEc : Energy level of the conduction bandThe expression \(\mathop \smallint \limits_{{E_c}}^\infty N\left( E \right)f\left( E \right)dE\) gives |
| A. | minimum number of electrons in conduction band |
| B. | concentration of electrons in conduction band |
| C. | energy of electron concentration in conduction band |
| D. | conductivity of electrons in conduction band |
| Answer» C. energy of electron concentration in conduction band | |
| 10. |
Arrange the following semiconductor materials on the basis of Energy - Bandgap (Eg) from highest to lowestA) ZnSeB) InAsC) CdTeD) GeE) InPChoose the correct answer from the options given below: |
| A. | D, C, B, A, E |
| B. | C, B, A, E, D |
| C. | B, A, D, C, E |
| D. | A, C, E, D, B |
| Answer» E. | |
| 11. |
A small percentage of impurity is added to an intrinsic semiconductor at 300 K. Which one of the following statements is true for the energy band diagram shown in the following figure? |
| A. | Intrinsic semiconductor doped with pentavalent atoms to form an n-type semiconductor |
| B. | Intrinsic semiconductor doped with trivalent atoms to form an n-type semiconductor |
| C. | Intrinsic semiconductor doped with pentavalent atoms to form a p-type semiconductor |
| D. | Intrinsic semiconductor doped with trivalent atoms to form a p-type semiconductor |
| Answer» B. Intrinsic semiconductor doped with trivalent atoms to form an n-type semiconductor | |
| 12. |
An intrinsic semiconductor has the following properties:1. Its electron concentration equals its hole concentration.2. Its carrier density increases with temperature.3. Its conductivity decreases with temperature. |
| A. | 1, 2 and 3 |
| B. | 2 and 3 only |
| C. | 1 and 3 only |
| D. | 1 and 2 only |
| Answer» E. | |
| 13. |
In a degenerately doped n-type semiconductor, the Fermi level lies in the conduction band when |
| A. | concentration of electrons in the conduction band exceeds the density of states in the valence band |
| B. | concentration of electrons in the valence band exceeds the density of states in the conduction band |
| C. | concentration of electrons in the conduction band exceeds the product of the density of states in the valence band and conduction band |
| D. | None of the above |
| Answer» C. concentration of electrons in the conduction band exceeds the product of the density of states in the valence band and conduction band | |
| 14. |
A silicon bar is doped with donor impurities ND = 2.25 × 1015 atoms / cm3. Given the intrinsic carrier concentration of silicon at T = 300 K is ni = 1.5 × 1010 cm-3. Assuming complete impurity ionization, the equilibrium electron and hole concentrations are |
| A. | n0 = 1.5 × 1016 cm-3, p0 = 1.5 × 105 cm-3 |
| B. | n0 = 1.5 × 1010 cm-3, p0 = 1.5 × 1015 cm-3 |
| C. | n0 = 2.25 × 1015 cm-3, p0 = 1.5 × 1010 cm-3 |
| D. | n0 = 2.25 × 1015 cm-3, p0 = 1 × 105 cm-3 |
| Answer» E. | |
| 15. |
For the following energy band diagram determine the approximate resistivity for x > L portion of semiconductor. Eg = 1.12 eV, T = 300 K, μn = 600 cm2/V-sec, μp = 400 cm2/V-sec, ni = 1010/cm3 |
| A. | 11.00 ohm-cm |
| B. | 15.75 ohm-cm |
| C. | 23 ohm-cm |
| D. | 31.25 ohm-cm |
| Answer» E. | |
| 16. |
If a donor type impurity is added to the semiconductor, then at a given temperature, the Fermi Level. |
| A. | Moves towards the centre of the energy gap |
| B. | Moves towards the valence band |
| C. | Moves towards the conduction band |
| D. | Doesn’t change |
| Answer» D. Doesn’t change | |
| 17. |
1 cm3 of pure Germanium at 20°C contains about 4.2 × 1022 atoms, 2.5 × 1013 free electrons, and 2.5 × 1013 holes. 0.001% of Arsenic doping donates an extra 1017 free electrons in the same volume. The approximate number of holes in one cm3 in the doped semiconductor under equilibrium condition is: |
| A. | 6.25 × 109 |
| B. | 2.5 × 109 |
| C. | 10.5 × 109 |
| D. | 1017 |
| Answer» B. 2.5 × 109 | |
| 18. |
Majority carriers of P type material |
| A. | Electrons |
| B. | Holes |
| C. | Protons |
| D. | None of the above |
| Answer» C. Protons | |
| 19. |
In terms of energy bands, semiconductors can be defined as those materials that have: |
| A. | Almost an empty conduction band and almost filled valence band with a very narrow energy gap between the conduction and valence band. |
| B. | Almost an empty conduction band and almost filled valence band with a very high energy gap between the conduction and valence band |
| C. | Almost and empty conduction band and low filled valence band with a very narrow energy gap between the conduction and valence band |
| D. | Almost full conduction band and almost filled valence band with a very narrow energy gap between the conduction and valence band |
| Answer» B. Almost an empty conduction band and almost filled valence band with a very high energy gap between the conduction and valence band | |
| 20. |
In a MOS capacitance fabricated on a P-type semiconductor, a strong inversion occurs, when potential is |
| A. | Equal to Fermi level |
| B. | Zero |
| C. | Negative and equal to Fermi potential in magnitude |
| D. | Positive and equal to Fermi potential in magnitude |
| Answer» E. | |
| 21. |
An exact position of Fermi level in an n-type semiconductor is |
| A. | \({E_C} - KT\ln \left[ {\frac{{{N_C}}}{{{N_D}}}} \right]\) |
| B. | \({E_C} + KT\ln \left[ {\frac{{{N_C}}}{{{N_D}}}} \right]\) |
| C. | \({E_C} - KT\ln \left[ {\frac{{{N_CN_V}}}{{{N_D}}}} \right]\) |
| D. | \({E_C} - KT\ln \left[ {\frac{{{N_C}}}{{{N_V}}}} \right]\) |
| Answer» B. \({E_C} + KT\ln \left[ {\frac{{{N_C}}}{{{N_D}}}} \right]\) | |
| 22. |
Forbidden energy gap in an atom is the gap between the: |
| A. | 2nd and valence band |
| B. | valence band and conduction band |
| C. | 1st and 2nd band |
| D. | 1st and valence band |
| Answer» C. 1st and 2nd band | |
| 23. |
Covalent bond energy in germanium is about |
| A. | 0.72 eV |
| B. | 31 eV |
| C. | 3.4 eV |
| D. | 20.4 eV |
| Answer» B. 31 eV | |
| 24. |
A Si sample is doped with 1017 Arsenic atoms/cm3. Displacement of EF relative to Ei is ______ |
| A. | Positive, 0.589 eV |
| B. | Negative, 0.589 eV |
| C. | Positive, 0.407 eV |
| D. | Negative, 0.407 eV |
| Answer» D. Negative, 0.407 eV | |
| 25. |
In an extrinsic semiconductor, the conductivity significantly depends on: |
| A. | Majority charge carriers generated due to impurity doping |
| B. | Minority charge carriers are generated due to thermal agitation. |
| C. | Majority charge carriers are generated due to thermal agitation. |
| D. | Minority charge carriers generated due to impurity doping. |
| Answer» B. Minority charge carriers are generated due to thermal agitation. | |
| 26. |
A single crystal intrinsic semiconductor is at a temperature of 300 K with an effective density of states for holes twice that of electrons. The thermal voltage is 26 mV. The intrinsic Fermi level is shifted from the mid-bandgap energy level by |
| A. | 18.02 meV. |
| B. | 9.01 meV. |
| C. | 13.45 meV. |
| D. | 26.90 meV. |
| Answer» C. 13.45 meV. | |
| 27. |
In n-type material, majority carriers would be |
| A. | Holes |
| B. | Dopants |
| C. | Slower |
| D. | Electrons |
| Answer» E. | |
| 28. |
A long-channel NMOS transistor is biased in the linear region with \(\rm V_{DS}=50\ mV\) and is used as a resistance. Which one of the following statements is NOT correct? |
| A. | If the device width W is increased, the resistance decreases. |
| B. | If the threshold voltage is reduced, the resistance decreases. |
| C. | If the device length L is increased, the resistance increases. |
| D. | If VGS is increased, the resistance increases. |
| Answer» E. | |
| 29. |
By doping Germanium with Gallium, the types of semi-conductors formed are:1. N-type2. P-type3. Intrinsic4. ExtrinsicWhich of the above are correct? |
| A. | 1 and 2 |
| B. | 2 and 4 |
| C. | 1 and 3 |
| D. | 2 and 3 |
| Answer» C. 1 and 3 | |