(SEM IV) THEORY EXAMINATION 2022-23 DIGITAL ELECTRONICS

This question paper belongs to B.Tech – Semester IV – Digital Electronics (KOE-049).
It carries 100 marks and the duration is 3 hours.

The exam tests the student’s understanding of:          Number systems and code conversions

Boolean algebra and logic simplification                     Combinational and sequential circuits

Flip-flops, counters, memory design                            Multiplexers, adders, PLAs, PALs

State diagrams and FSM behavior                                Logic families and their characteristics

The paper is divided into three structured sections – A, B, and C.

2. Section A – Short Conceptual Questions (20 Marks)

This section contains 10 questions, each of 2 marks, requiring brief and precise answers.

The topics include:

● Number System Conversions

Binary → Gray code, Excess-3 code.

● Subtraction Using Complements

Binary subtraction via 1’s and 2’s complement.

● Serial vs Parallel Adder

Speed and hardware comparison.

● Multiplexer Cascading

How many 4×1 MUX are needed to build a 64×1 MUX.

● Characteristic vs Excitation Table

Difference in usage for flip-flop design.

● Combinational vs Sequential Circuits

Dependency on inputs vs past states.

● Address Lines for 8K Memory

Memory size and address line calculation.

● Propagation Delay

Definition of gate delay.

● Race-Around Condition

Issue in JK flip-flop due to level-triggering.

● PAL vs PLA

Structural and functionality differences.

This section evaluates fundamentals and theoretical clarity.

3. Section B – Long Descriptive Questions (30 Marks)

Students must attempt any three questions, each of 10 marks.

This section requires explanation, diagrams, truth tables, and logic design.

Topics include:

● Boolean Function Implementation

Realizing functions using NAND gates only.

● Full Adder Design

Designing a full adder, using half adders and NAND-only realization.

● Excitation Tables

For SR, JK, T, and D flip-flops—used in sequential circuit design.

● Memory System Design

Creating an 8K×8 RAM using 1K×8 memory ICs.

● Mealy vs Moore FSM

Operational difference with diagrams and examples.

This section tests circuit design skills, theoretical understanding, and logical reasoning.

4. Section C – Application-Based & Advanced Questions (50 Marks)

Section C contains five parts (Q3–Q7).
From each part, the student must attempt one question, each of 10 marks.

Part 3 – Boolean Minimization

Choice between:

● K-map Simplification

Simplifying expression, drawing groups, and implementing the logic circuit.

OR

● Tabulation Method

Using Quine–McCluskey method for multi-variable minimization.

Part 4 – Adders & Comparators

Choice between:

● BCD Adder Design

Using a 4-bit binary parallel adder with correction logic.

OR

● 2-bit Magnitude Comparator

Drawing block diagram and logic implementation.

Part 5 – Counter + Flip-Flop Design

Choice between:

● MOD-10 Synchronous Counter

Design using flip-flops and defining state transitions.

OR

● JK Flip-Flop Analysis

State table, equation, and state diagram.

Part 6 – Logic Families & Implementation

Choice between:

● Why ECL is Better

High speed advantages + NAND implementation using DTL/TTL.

OR

● Logic Family Characteristics

Noise margin, fan-in, fan-out + CMOS NAND implementation.

Part 7 – Sequential Circuit Design / State Reduction

Choice between:

● State Reduction & Assignment

Minimizing number of states with example.

OR

● Sequential Circuit with Two Flip-Flops

For input X with specific state transitions (00 → 01 → 11 → 10 → 00 ...).

This section tests design thinking, advanced circuit knowledge, and FSM modeling.

Final Summary (Purpose of WHAT DESCRIPTION)

This WHAT DESCRIPTION provides a complete, long, section-wise explanation of:

Structure of the question paper

Purpose of each section

Type of questions asked

Topics expected from the student

How the paper evaluates knowledge of Digital Electronics

It helps understand the entire format and intention of the KOE-049 exam.