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Sample Exam Paper

MPY351Sample Practical Examination — II

Course: Electronics Lab (MPY351)Programme: M.Sc. Physics (Electronics Specialization) — Semester III
Time: 4 HoursMaximum Marks: 100

General Instructions:

  1. The examiner will allot one device-characterization experiment and one timer/oscillator circuit experiment.
  2. Bring your completed lab record; unrecorded experiments will not be evaluated.
  3. Handle MOSFET devices with ESD (electrostatic discharge) precautions at all times.
  4. A viva-voce covering the theory of both allotted experiments will follow the practical.

Section A — Short Answer (Compulsory)

  1. Why must a MOSFET be handled with electrostatic discharge precautions? (2 marks)
  2. What is the difference between an astable and a monostable multivibrator? (2 marks)
  3. State the frequency formula for a Wien-bridge oscillator using an op-amp. (2 marks)
  4. What is the purpose of a biased clipper circuit? (2 marks)
  5. Define pinch-off voltage and saturation drain current for an FET. (2 marks)
  6. Describe, in brief, the basic building blocks of a fibre-optic communication link. (2 marks)
  7. Why is amplitude stabilization needed in a Wien-bridge sine-wave oscillator? (2 marks)

Section B — Attempt any two parts of each

  1. Plot the drain and transfer characteristics of the given FET and determine its pinch-off voltage and IDSS. (5 marks)
  2. Set up the 555 timer IC in astable mode; observe the output waveform and verify the theoretical frequency against your measurement. (5 marks)
  3. Set up a Hartley oscillator on the breadboard and measure its output frequency; compare with the calculated value. (5 marks)
  4. Study the characteristics of the given phototransistor at three different illumination levels and plot the resulting I-V curves. (5 marks)

Section C — Attempt any two questions in full

  1. Explain the construction and working of the MOSFET, distinguishing between depletion-mode and enhancement-mode operation, and describe how its characteristic curves are obtained experimentally. (10 marks)
  2. Describe in detail the operation of the 555 timer IC in both astable and monostable modes, deriving the relevant timing equations. (10 marks)
  3. Explain the working principle of a phototransistor and describe a simple fibre-optic communication link experiment, covering the roles of the transmitter, fibre and receiver. (10 marks)