About this previous year paper
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.