(SEM IV) THEORY EXAMINATION 2023-24 DIGITAL ELECTRONICS

This document is a B.Tech (Semester IV) Theory Examination Question Paper for the subject BEE401 – Digital Electronics, conducted for the academic session 2023–2024.
It is a 3-hour, 70-mark examination designed to assess students’ understanding of number systems, logic gates, combinational and sequential circuits, logic families, flip-flops, multiplexers, ADC/DAC, and digital system design.
 

The paper is divided into three sections—A, B, and C—ranging from short conceptual questions to advanced circuit design questions.

SECTION A – Short Answer Questions (14 Marks)

Seven 2-mark questions on fundamental digital electronics topics:

Decimal-to-binary conversion (37₁₀ → binary)

Explanation of Universal Gates (NAND, NOR)

Meaning of Combinational Circuit

Definition of Half Adder

Advantages & disadvantages of ECL Logic Family

Meaning of Fan-in and Fan-out

Advantages of CMOS Logic Family

These questions evaluate basic definitions, functions, and digital logic fundamentals.

SECTION B – Intermediate-Level Circuit Design & Logic Problems (21 Marks)

Students must attempt any three of the following:

Simplification of Boolean expression:
F(A,B,C,D) = Σm(1,3,7,11,15) + d(0,2,5)

Design of 32:1 Multiplexer using 8:1 and 4:1 MUX

State table, state diagram, and state equation for Clocked JK Flip-Flop

Operation of TTL NAND gate in tri-state configuration

Implementation + operation of 3-input NOR Gate using CMOS and DTL logic families

These problems test circuit design ability, Boolean simplification, and understanding of digital logic families.

SECTION C – Advanced Digital Electronics Questions (28 Marks)

Each question contains two options; one must be attempted from each.

3. Boolean Expression Conversions & K-Map Minimization

Convert expressions to Standard POS Form:
(i) AB + AC + BC
(ii) A + BC + ABC

Minimize SOP expression using K-map:
Y = A̅B̅C̅ + A̅BC̅ + A̅BC + AB̅C

4. Algorithm & Multiplexer Logic

Flowchart showing subtraction algorithm using Adder

Implement F(A,B,C,D) = Σm(0,2,3,6,8,11,12,14) using Multiplexer

5. Sequential Logic – Flip-Flops & Shift Registers

Working of Master–Slave JK Flip-Flop with logic diagram

Modes of operation & applications of Shift Register

6. Logic Family Comparison & CMOS Gate Operation

Performance comparison of TTL, CMOS, ECL Logic Families

Operation of CMOS NAND and CMOS NOR with neat diagrams

7. Data Converters (ADC/DAC)

Meaning + working of R-2R Ladder DAC

Types of ADCs and operation of Dual Slope ADC

This section evaluates deep understanding of sequential circuits, ADC/DAC design, multiplexer-based implementation, and advanced logic family behavior.

Overall Purpose of the Document

This exam paper evaluates a student's complete understanding of:

Number systems and Boolean algebra

Logic gates (TTL, CMOS, ECL)

Combinational circuits (MUX, adder, NOR, POS/SOP forms)

Sequential circuits (JK flip-flop, shift registers)

K-map simplification

Algorithmic flowcharts

Data converters (ADC, DAC)

Circuit design using digital logic families

The paper includes numerical conversions, logic simplification, diagrams, state modeling, and implementation-based questions—ensuring a full assessment of digital electronics knowledge.