InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The collector current for a transistor is `6.6mA`, and its current gains `alpha` is `0.95`. Determine `I_(B)` and `beta` |
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Answer» Correct Answer - `0.35mA, 19` |
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| 2. |
The base current of a transistor is 0.105 mA and collector current is `2.05mA`. Determine the value of `beta, I_(e)` and `alpha` A change of `27muA` in the base current produces a change of 0.65 mA in the collector current. Find `beta_(a.c.)`. |
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Answer» Correct Answer - (i) `19.52, 2.155mA, 0.95` (ii) `24.07` |
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| 3. |
A crystal diode having internal resistance `200Omega` is used as a half rectifier. If the applied voltage is `V=50 sin omegat` volt and load resistance is `800Omega`, find (i) maximum output current (ii) d.c. output current (iii) d.c. output power and (iv) d.c. output voltage. |
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Answer» Correct Answer - (i) `61mA` (ii) `19.4mA` (iii) `0.301W` (iv) `15.52V` |
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| 4. |
Find the current through the circuit and the potential difference across the diode shown in fig. The drift current for the diode is `20muA` |
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Answer» Correct Answer - `15muA, ~~4.0V` |
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| 5. |
In the circuit shown in fig the base current `I_(B)=5.0muA`, base resistor `R_(B)=1.0MOmega` collector resistor `R_(c)=1.0kOmega` the collector current `I_(C)=5.0mA` and the d.c. voltage in the collect circuit `V_("CC")=6.0V`. (i) Can this circuit be used as an ampifier? (ii) What happens if the resistance `R_(C)` is `400Omega` and `I_(B), I_(C)` and `i_(C)` and `R_(B)` remain same as above? |
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Answer» Correct Answer - (i) No (ii) Can be used as ampifier |
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| 6. |
In a transistor circuit shown in fig, `R` has a resistance of `150kOmega, R_(L)` has a resistance of `750Omega`, and the direct current gain of the transistor is 80. Assuming ther is negligible potential difference between `B` and `E`, calculate (a) the base current rent `I_(B)` and (b) the potential difference betwen the collector and emitter. |
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Answer» Correct Answer - `6xx10^(-5)A, 5.4V` |
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| 7. |
A sinusoidal voltage of rms value `220V` is applied to a diode and a resistor `R` in the circuit shown in fig. Show that half wave rectifaction occurs. If the diode is ideal, what is the rms voltage across? |
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Answer» Correct Answer - `110sqrt(2)V` |
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| 8. |
Find the equivalent resistnace of the circuit shown in fig between the points `A` and `B` |
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Answer» Correct Answer - `10Omega` if `V_(A)gtV_(B)` and `20Omega` if `V_(A)lt V_(B)` |
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| 9. |
As shown in fig an amplifier of no load gain 400 and input resistance `100Omega` is connected to external signal via a series resistance of `300Omega`. What is the apparent voltage gain? |
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Answer» Correct Answer - 100 |
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| 10. |
For a `CB` amplifier the input resistance is `800Omega` and the output resistance is `600 k Omega` (a) Determine the voltage gain if the emitter current is `12mA` and `alpha=0.97` (b) What is the power gain? |
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Answer» Correct Answer - `727.5, 706` |
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| 11. |
A doped semiconductor has impurity levels `30meV` below the conduction band. Is the material `n`-type or `p`- type? Find the maximum wavelength of ight so that an electron of impurity level is just able to jump to into conduction band. |
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Answer» Correct Answer - `4.125xx10^(-5)m` |
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| 12. |
The bank gap of an alloy semiconductor galiumarseide phosphie is `1.98eV`. Calculate the wavelength of radiation that is emitted when electrons and holes in this material combine directly. What is the colour of the emitted radiation? Take `h=6.6xx10^(-34) Js` |
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Answer» Correct Answer - `6250Å,` red |
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| 13. |
Germanium is doped one part million with indium at room temperature. Calculate the conductivity of doped germanium. Given: concentration of Ge atoms `=4.4xx10^(28)m^(-3)`, intrinsic carrier concentration `(n_(i))=2.4xx10^(19)m^(-3), mu_(e)=0.39m^(2)V^(-1)s^(-1)` and `mu_(k)=0.19m^(2)V^(-1)s^(-1)` |
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Answer» Correct Answer - `1.34xx10^(3)ohm^(-1)m^(-1)` |
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| 14. |
Figure Shows a diode connected to an external resistance and an e.m.f. Assuming that the barrier potential developed in diode is `0.5 V`, obtain the value of current in the circuit in milliampere. |
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Answer» Correct Answer - `40mA` |
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| 15. |
In a photodiode the coductivity increases when the material is exposed to light. It is found that coductivity change only if the wavelength is less than `600nm`. What is the band gap? |
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Answer» Correct Answer - `1.995eV` |
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| 16. |
Determine the number density of donor atoms which have to be added to an intrinsic germanium to produce an `n`-type semiconductor of conductity `0.06Sm^(-1)`. Given the mobility of electrons `=0.39m^(2)V^(-1)s^(-1)`. Neglect the contribution of holes to the conductivity. |
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Answer» Correct Answer - `96x10^(16)m^(-3)` |
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| 17. |
A potential barrier of `0.60 V` exists across a p-n junction. If the depletion region is `6.0x10^(-7)m` wide, what is the intensity of the electric field in this region. An electron with speed `5.0x10^(5) ms^(-1)` approaches the p-n junction from the n-side, with what speed will it enter p-side. |
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Answer» Correct Answer - (i) `1.0xx10^(8)Vm^(-1)` (ii) `2.0xx10^(5)ms^(-1)` |
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