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.
