Electronic Devices 2025 — 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

    During the reverse biased of the diode, the back resistance decrease with the ________ of the temperature.

    Free sample

    Answer: increase

    Explanation

    As temperature increases, more minority charge carriers are generated due to thermal excitation, which increases the reverse saturation current and consequently decreases the reverse (back) resistance.

  2. II

    The amount of photo generated current increases slightly with an increase in ________.

  3. III

    The capacitance of a reverse biased PN junction ________ as reverse bias is decreased.

  4. IV

    In a PN junction with no external voltage, the electric field between acceptor and donor ion is called ________.

  5. V

    The free electron density in a conductor is (1/1.6)×1022/cm3(1/1.6) \times 10^{22} /\text{cm}^3 the electron mobility is 10 cm2/Vs10\ \text{cm}^2/\text{Vs}. Calculate the value of resistivity ________ .

  6. VI

    If Φs\Phi s and ΦF\Phi F denotes respectively the surface & Fermi potential, strong inversion takes place in n channel MOSFET, when ________.

  7. VII

    The greatest wavelength of photons that a photodiode built of a semiconductor with a bandgap of 2eV can detect is around ________ nm.

  8. VIII

    Example of direct band gap semiconductor is ________.

  9. IX

    When the diode is reverse biased with a voltage of 6V and Vbi=0.63VV_{bi}=0.63V. Calculate the total potential.

    TEXT
     +--------|>|---------+
 |       1BH62        |
(+)                   |
 V1                   V
(-)                   
12 V                  |
 |                    |
 +--------------------+
    Show answer to question IX
  10. X

    BJT is used as a switch is operated in ________ region.

  11. XI

    The gate to source voltage of a MOSFET with threshold voltage 400mV in saturation is 900mV for drain current of 1mA . The drain current for VGS=1400mVV_{GS} = 1400mV is ________.

  12. XII

    Which type of photodetector is based on the principle of internal photoemission?

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

  1. 2

    What are direct band gap & indirect band gap semiconductors? Draw E-K diagram for Si and GaAs.

  2. 3

    Derive the expression for drain current for an ideal MOSFET at saturation.

  3. 4

    Draw and explain the output characteristics of BJT in CB configuration.

  4. 5

    What is meant by dc operating point or Q point in a transistor characteristic? What is load line?

  5. 6

    If the transconductance parameter is 2mA/V22mA/V^2 for VGS=1VV_{GS} = 1V & Vt=0.5VV_t = 0.5 V calculate the linear resistance rDSr_{DS}. Also mention the region of operation if VDS=1VV_{DS} = 1V.

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

  1. 7(a)

    Write down the mathematical expression for Fermi-Dirac probability function and plot f(E) Vs EfE_f for three different temperatures T= 0K, 300 K & 2000 K.

    5 marks
  2. 7(b)

    Explain different scattering mechanisms in semiconductor devices.

    5 marks
  3. 7(c)

    Explain with E-K diagram, why LED emits light but pn-junction does not?

    5 marks
  4. 8(a)

    Which of the two semiconductor materials between Si or Ge has larger conductivity at room temperature and why?

    5 marks
  5. 8(b)

    What is an Ohmic contact?

    3 marks
  6. 8(c)

    Can a Schottky diode be used as Ohmic contact ? Explain in brief.

    5 marks
  7. 8(d)

    Draw the symbol and I-V characteristics of a Zener diode.

    2 marks
  8. 9(a)

    Explain the various modes of operation possible in a BJT.

    5 marks
  9. 9(b)

    With the help of circuit diagram describe the operation of BJT in CE configuration.

    10 marks
  10. 10(a)

    Explain the band bending and channel inversion in case of NMOS.

    10 marks
  11. 10(b)

    What is channel length modulation.

    5 marks
  12. 11(a)

    What is mobility and conductivity. Define effective mass. Derive relationship between energy & momentum.

    5 marks
  13. 11(b)

    Define mobility and write down its unit. Also give an expression that relates the mobility and diffusivity of carriers in a semiconductor. State the significance of this equation.

    5 marks
  14. 11(c)

    A Si sample A is doped with 1018 atoms/cm310^{18} \text{ atoms/cm}^3 of Boron. Another sample B of identical dimensions is doped with 1018 atoms/cm310^{18} \text{ atoms/cm}^3 of Phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of sample A to sample B.

    5 marks

About this paper

The MAKAUT Electronic Devices (EC-301) 2025 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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Why solve Electronic Devices PYQs?

Frequently asked questions

5 questions

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 2025 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.

Are there solutions for this paper?

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