(SEM III) THEORY EXAMINATION 2018-19 ENVIRONMENT AND ECOLOGY

The uploaded file is a B.Tech Semester III Theory Examination Paper (2018–2019) for the subject ELECTRONICS DEVICES AND CIRCUITS, with Subject Code REC 302.
The document contains 2 pages, carries a total of 70 marks, and the exam duration is 3 hours.

This question paper is designed for engineering students studying the fundamentals of semiconductor devices, diode and transistor behavior, MOSFET characteristics, amplifier circuits, oscillators, and electronic feedback systems. It tests both theoretical understanding and analytical thinking in electronic circuits.

PAGE 1 — OVERVIEW & CONTENT

Page 1 includes the exam header and SECTION A, which contains short-answer questions worth 14 marks (2 marks × 7 questions).

SECTION A Topics Include:

Semiconductors & Luminescence

Types of semiconductor materials used for luminescence effect (e.g., direct bandgap semiconductors like GaAs, GaN).

Diffusion of Carriers

Concept of carrier movement from high concentration to low concentration.

MOSFET Characteristics

Why MOSFET drain current in the linear region decreases with temperature increase.

Threshold Voltage

Basic definition and importance in MOSFET operation.

Zener Breakdown vs Avalanche Breakdown

The behavior of diodes under high reverse voltage.

JFET Small Signal Model

Diagram and explanation of small-signal parameters.

Transconductance

Meaning and role in amplifiers.

These questions test understanding of semiconductor physics and basic device concepts.

PAGE 2 — DETAILED QUESTIONS (SECTION C)

Page 2 contains long-answer questions worth 7 marks each. Students must attempt one part from each question group.

QUESTION 6 — MOSFET & Amplifier Design

(a)

Explain:

Single-stage MOS amplifier                 MOSFET internal capacitances such as:

Students must describe:                                           Amplifier configuration

How capacitances affect frequency response          Gain characteristics

Use of small-signal models

(b)

Draw and explain a biasing circuit of a MOSFET amplifier, including:

Circuit diagram                                      Selection of Q-point

Voltage divider biasing                          Stability and linearity considerations

This question tests circuit design skills and understanding of MOSFET operation.

QUESTION 7 — Oscillators & Feedback Topologies

(a)

Draw the LC Oscillator circuit diagram and explain:

Tank circuit (L & C)                                                          Positive feedback requirement

Barkhausen Criterion for sustained oscillation             Frequency of oscillation formula

(b)

Explain four feedback topologies with diagrams:

Students must describe:

How feedback improves amplifier performance

Effect on gain, bandwidth, stability, and distortion

OVERALL SUMMARY OF THE DOCUMENT

This exam paper thoroughly covers essential topics in analog electronics, including:

Semiconductor materials & carrier transport             Diode & breakdown mechanisms

JFET small-signal modeling                                        MOSFET device physics & biasing

Amplifier concepts                                                     Internal capacitances and AC response

LC oscillators                                                              Feedback topologies

The paper is ideal for:

B.Tech Electronics & Communication (ECE)               Electrical Engineering

Computer Engineering (EC-related subjects)

Students preparing for exams or strengthening electronic fundamentals