(SEM IV) THEORY EXAMINATION 2022-23 ANALOG ELECTRONICS

This document is a B.Tech (Semester IV) Theory Examination paper for the course KOE047 – Analog Electronics, academic session 2022–2023.
It is a 3-hour, 100-mark exam designed to test a student's understanding of analog circuits, transistor biasing, feedback amplifiers, oscillators, op-amp applications, filters, and current mirror circuits.

The exam is divided into three sections:
SECTION A – Short, conceptual questions
SECTION B – Medium-length analytical & derivation-based questions
SECTION C – Long, design-oriented & numerical questions

The paper includes definitions, derivations, circuit analysis, frequency calculations, and design problems.

SECTION A – Short Answer Questions (20 Marks)

Ten 2-mark questions covering fundamental analog electronics concepts:

Difference between DC analysis vs AC analysis

Definition of stability factor in biasing

Definition of power amplifier efficiency

Calculate CMRR (in dB) given differential gain = 1000 & common-mode gain = 10

Calculate closed-loop gain for negative feedback (A = 2000, β = 0.02)

Concept of virtual short in op-amps

Properties of ideal op-amp

Meaning of frequency stability in oscillators

Difference between Comparator vs Schmitt Trigger

Definition of Filter

This section tests theoretical clarity and basic computational skills.

SECTION B – Medium-Length Analytical Questions (30 Marks)

Attempt any three (10 marks each):

(a) Emitter Follower

Operation of emitter follower                               Derivation of input resistance

Derivation of output resistance

(b) Negative Feedback Advantages

Comprehensive explanation of how feedback improves:

Gain stability                                      Bandwidth

Noise reduction                                 Distortion reduction

(c) Tank Circuit & Colpitts Oscillator

Explain LC tank circuit

Derive:

Frequency of oscillation for Colpitts oscillator

Gain condition for sustained oscillations

(d) Op-Amp Applications

Explain:

Precision rectifier                              Phase changer

Averaging amplifier                          Non-inverting summer

(e) Super Diode & Precision Rectifier

Concept of Super Diode using op-amp + diode

Working of full-wave precision rectifier

Transfer characteristics

SECTION C – Long Answer Questions (50 Marks Total)

Each question has two choices; attempt one from each.

3. Transistor Biasing / MOSFET Capacitances (10 Marks)

Option (a)

Definition of stability factor                         Need for transistor biasing

Explain voltage-divider bias in detail

Option (b)

MOSFET internal capacitances

High-frequency equivalent circuit model of MOSFET

4. Feedback Amplifier / Class-B Amplifier (10 Marks)

Option (a)

Describe shunt–series feedback amplifier

Derive formula for output resistance with feedback

Show how negative feedback reduces output resistance

Option (b)

Class-B amplifier working                                 Circuit diagram

Transfer characteristics                                     Derivation of power conversion efficiency

5. RC Phase Shift Oscillator / Op-Amp Square Wave Generator (10 Marks)

Option (a)

RC phase-shift oscillator circuit

Derive expressions for:                               Frequency of oscillation

Gain requirement for sustained oscillations

Option (b)

Op-amp square-wave generator              Neat circuit diagram

Calculate its time period

6. Current Mirror / BJT Differential Amplifier (10 Marks)

Option (a)

Desirable characteristics of current mirror             Draw simple BJT current mirror

Derive current transfer ratio assuming matched transistors

Option (b)

Circuit of BJT differential amplifier

Derive:

Input differential resistance                             Differential voltage gain

7. Filter Design / Filter Terminology (10 Marks)

Option (a)

Define filter circuit

Classification based on frequency response (LPF, HPF, BPF, BSF)

Design second-order High-Pass Filter:

Cut-off frequency = 1 kHz

Passband gain = 2

Option (b)

Explain key filter terms:

Pass Band                   Stop Band

Roll-off rate                Cut-off frequency

Overall Purpose of the Document

This exam paper evaluates student competency in:

Analog Circuit Analysis

DC/AC analysis, small-signal models.

Transistor & MOSFET Behavior

Biasing, stability, internal capacitances.

Feedback & Stability

Negative feedback effects on gain & resistance.

Oscillators

Tank circuits, RC phase shift, Colpitts oscillator.

Operational Amplifiers

Applications like precision rectifier, phase changer, summers, comparators, square-wave generators.

Filters & Frequency Response

High-pass filter design, classification, key terminology.

Current Mirrors & Differential Amplifiers

The paper includes circuit derivations, formula-based calculations, design problems, and conceptual understanding, giving a complete evaluation of Analog Electronics.