Electronic Devices 2024 — MAKAUT · EC-301 · Mid Sem PYQ with solutions

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Maulana Abul Kalam Azad University of Technology

Solutions

31 answers across 3 groups

Try each question first, then open it to check your answer.

Group AVery Short Answer Type Question · answer any 10 · 1 mark each

  1. I

    Density gradient produces ___________ force on majority carriers.

    Free sample

    Answer: diffusion

  2. II

    Which region of a bipolar junction transistor (BJT) is smallest?

  3. III

    What condition makes MOSFET a Transconductance device?

  4. IV

    What do you mean by conversion efficiency of a solar cell?

  5. V

    Write the name of the best and most widely used semiconductor.

  6. VI

    What type of carriers takes part in current conduction through a Schottky diode?

  7. VII

    If a transistor is to be used as a switch, which region/s is/are the region/s of operation?

  8. VIII

    At VGS=0V_{GS} = 0, the channel of depletion MOSFETs works like _______________.

  9. IX

    The interconnections are made during _______________.

  10. X

    At absolute zero, semiconductor crystal behaves like a/an _______________.

  11. XI

    What is Boltzmann approximation in a zero-biased pn junction?

  12. XII

    What does Ebers Moll model state?

Group BShort Answer Type Question · answer any 3 · 5 marks each

  1. 2

    Find the expression for open circuit voltage of a pn junction solar cell with photocurrent ILI_L and reverse saturation current IsI_s.

  2. 3

    Distinguish between insulator, semiconductor and metal on the basis of energy band diagrams.

  3. 4

    Draw the small signal equivalent circuit of a normal pn junction diode. Explain the origin of diffusion resistance in that circuit.

  4. 5

    Draw the input characteristics of a transistor in common emitter (CE) mode. Explain why the current on the same characteristics decreases with increase in the corresponding output parameter.

  5. 6
    • a) What are density of states and Fermi function?
    • b) Explain the plot of Fermi-Dirac distribution function with energy for different temperature.
    Show answer to question 6

Group CLong Answer Type Question · answer any 3 · 15 marks each

  1. 7(a)

    Derive the expression for built in potential of a pn junction.

    6 marks
  2. 7(b)

    Draw the energy band diagram of a pn junction under forward bias. Derive the relation np0=nn0exp⁡(−eVbi/kT)n_{p0} = n_{n0} \exp(-eV_{bi}/kT).

    5 marks
  3. 7(c)

    The n side of a silicon pn junction has a doping level of 5×1016 cm−35 \times 10^{16} \text{ cm}^{-3}.

    A forward bias of 0.55 V is applied on the pn junction.

    Determine the minority carrier concentration at the edge of the space charge region.

    Assume that the pn junction is at 300 K and ni=1.5×1010 cm−3n_i=1.5 \times 10^{10} \text{ cm}^{-3}.

    Take kT/e=0.026 VkT/e=0.026 \text{ V}.

    Show answer to question 7(c)4 marks
  4. 8(a)

    Discuss the basic principle of operation of a bipolar junction transistor.

    6 marks
  5. 8(b)

    Draw the energy band diagram of a zero biased transistor. Explain the diagram.

    4 marks
  6. 8(c)

    Draw the circuit diagram for obtaining the input characteristics of an npn transistor in common base (CB) mode. Discuss the steps to operate the circuit and plot the characteristics.

    5 marks
  7. 9(a)

    What do you mean by transfer characteristic of a MOSFET. Draw the transfer characteristics of enhancement and depletion type MOSFETs.

    6 marks
  8. 9(b)

    Obtain the small-signal equivalent circuit of a MOSFET from its basic geometry. Then draw and explain the simplified small-signal equivalent circuit valid at low frequency from it.

    6 marks
  9. 9(c)

    Explain the effect of source resistance in the simplified, low-frequency small-signal equivalent circuit.

    3 marks
  10. 10(a)

    Define absorption coefficient. Write the expression for the generation rate of electron–hole pairs due to photons.

    4 marks
  11. 10(b)

    Derive the expression for maximum power output of a photovoltaic cell.

    5 marks
  12. 10(c)

    How does series resistance affect the conversion efficiency of a photovoltaic cell?

    A p-n junction solar cell is fabricated using silicon and has the following important parameters:

    NaN_a3×1018 cm−33 \times 10^{18} \text{ cm}^{-3}NdN_d2×1016 cm−32 \times 10^{16} \text{ cm}^{-3}
    DnD_n25 cm2/s25 \text{ cm}^2/\text{s}DpD_p10 cm2/s10 \text{ cm}^2/\text{s}
    τn0\tau_{n0}4×10−7 s4 \times 10^{-7} \text{ s}τp0\tau_{p0}10−7 s10^{-7} \text{ s}

    The photocurrent density JL=20 mA/cm2J_L = 20 \text{ mA/cm}^2. Calculate the open-circuit voltage of the solar cell at T=300 KT = 300\text{ K}. Assume ni=1.5×1010 cm−3n_i = 1.5 \times 10^{10} \text{ cm}^{-3}.

    Show answer to question 10(c)6 marks
  13. 11(a)

    Derive the expression for electric field in the space charge region of a pn junction under zero bias. Find the built in potential from that in terms of the distances from the metallurgical junction.

    9 marks
  14. 11(b)

    Discuss the diffusion capacitances in the small signal equivalent circuit of a pn diode and find the expression for it.

    6 marks

About this paper

The MAKAUT Electronic Devices (EC-301) 2024 Mid Sem previous year question paper, set in semester 3. Download the verified PDF or read it online, then check your answers against the worked solutions above.

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Frequently asked questions

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What is the subject code for Electronic Devices?

EC-301 is the MAKAUT subject code for Electronic Devices.

Which exam is this Electronic Devices question paper from?

The MAKAUT 2024 Mid Sem exam, semester 3. A student shared it, and it was checked before publishing.

Which branches is this Electronic Devices paper for?

B.Tech Electronics and Communication Engineering.

Where can I find more EC-301 question papers?

On the Electronic Devices subject page, which collects every year's papers along with notes and the syllabus.

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