(SEM IV) THEORY EXAMINATION 2023-24 ANALOG ELECTRONICS CIRCUITS

This document is a B.Tech (Semester IV) Theory Examination paper for the course BOE408 – Analog Electronics Circuits, conducted for the academic year 2023–2024.
It is a 3-hour, 70-mark examination designed to evaluate students’ understanding of analog electronic devices, transistor biasing, amplifier configurations, feedback concepts, oscillators, differential amplifiers, op-amp circuits, current mirrors, and waveform generation.

The paper includes short conceptual questions, analytical descriptions, numerical problems, diagram-based questions, and design-oriented questions.

SECTION A – Short Answer Questions (14 Marks)

Seven questions worth 2 marks each. These test basic theoretical knowledge:

Functions of a diode in electronic circuits

Definition of voltage amplifier & current amplifier

Gain margin & phase margin in amplifier stability

Example of a non-sinusoidal oscillator

Meaning of CMRR in differential amplifiers

Definition of ICMR (Input Common Mode Range)

Ideal characteristics of an op-amp

These questions assess fundamental electronic concepts.

SECTION B – Medium-Length Analytical Questions (21 Marks)

Students must attempt any three out of five:

a. Fixed Bias Configuration of BJT Amplifier

Explanation of circuit, working, advantages (simple design) and disadvantages (poor stability).

b. Cascode Amplifier

Structure (CE + CB stages), high gain, high bandwidth, and improved isolation.

c. Oscillator Basics + Barkhausen Criterion + Numerical

Definition of oscillator

Conditions for sustained oscillations              RC-phase shift oscillator with:

R = 100 kΩ                                                     C = 600 pF
Calculation of frequency of oscillation.

d. Differential Amplifier Principle

How differential input is amplified, common-mode noise rejection, and output voltage expression.

e. Inverting Op-Amp Amplifier (Design + Derivation)

Gain expression: Av=−RfRinA_v = -\frac{R_f}{R_{in}}Av​=−Rin​Rf​​

Design of an inverting amplifier with:

Gain = –5                          Input resistance = 10 kΩ

This section tests deeper understanding + numerical application.

SECTION C – Long, Design-Oriented & Diagram-Based Questions (35 Marks)

Each question has two options, attempt one from each.

3. Transistor Amplifiers – CE Configuration / Biasing (7 Marks)

Option (a)

Explain Common-Emitter (CE) configuration:

High voltage gain                         180° phase shift

Input/output characteristics

Option (b)

Purpose of biasing, and self-biasing in FET amplifiers.

4. Class C Amplifiers / Voltage-Series Feedback (7 Marks)

Option (a)

Operation of Class C amplifier, conduction angle < 180°, high efficiency, typical RF applications.

Option (b)

How voltage-series feedback affects amplifier:

Gain decreases                      Bandwidth increases

Distortion reduces                Stability improves

5. Oscillators – Wien Bridge / Hartley (7 Marks)

Option (a)

Working, advantages, and limitations of Wien Bridge Oscillator.

Option (b)

Structure and oscillation generation of Hartley Oscillator using tapped inductors.

6. Op-Amp Gain Stage Design / Current Mirror (7 Marks)

Option (a)

Design considerations of high-gain op-amp stages, stability techniques.

Option (b)

Current mirror topology, circuit diagram and working—constant current output despite load variations.

7. Summing Amplifier Output / Precision Rectifier (7 Marks)

Option (a)

, calculate output voltage using superposition & inverting gain formula.

Option (b)

Design & working of precision full-wave rectifier using op-amp.

Overall Purpose of the Document

This exam paper thoroughly evaluates student skills in:

Analog Device Fundamentals

Diodes, BJTs, FETs, op-amps.

Amplifier Theory & Design

Biasing, CE configuration, differential amplifiers, op-amp applications.

Feedback and Stability

Gain margin, phase margin, voltage-series feedback effects.

Oscillator Circuits

RC phase-shift, Wien bridge, Hartley oscillator, Barkhausen criterion.

Waveform Generation & Rectification

Precision rectifiers, summing amplifiers, waveform calculation.

Current Mirrors & Transistor Operations

Basic topology, operation, and applications.

Overall, the paper includes definitions, formulas, derivations, circuit diagrams, frequency calculations, and design problems, ensuring complete assessment of Analog Electronics Circuits.