This question paper belongs to B.Tech Semester IV – Digital Electronics (KEE-401).
It carries 100 marks and the duration is 3 hours.
The exam evaluates a student's understanding of: Boolean algebra
Logic gates and their implementations Combinational circuits
Sequential circuits Flip-flops, counters, registers
CMOS/DTL logic families State diagrams, FSM design
The paper is divided into three sections: A, B, and C, each testing different levels of knowledge.
2. Section A – Short Answer / Conceptual Questions (20 Marks)
Section A contains 10 brief questions, each of 2 marks, covering essential definitions and conceptual clarity.
Topics involved include:
● Duality Principle
Explaining Boolean duality + proving AND (positive logic) ≡ OR (negative logic).
● EX-NOR Gate Implementation
Understanding EX-NOR logic and realizing it using minimum NOR gates.
● Half Adder
Explaining sum & carry logic, and designing using NAND gates.
● Combinational vs Sequential Circuits
Differences based on memory, timing, and output dependency.
● Synchronous vs Asynchronous Circuits
Clock dependency, hazards, timing issues.
● Multivibrators
Astable & Bistable operations.
● PISO Shift Register
Parallel-in, serial-out working concept.
● Static & Dynamic Hazards
Glitches caused by circuit propagation delays.
● Noise Margin
Tolerance range of logic levels.
● Advantages of CMOS
Low power, high noise immunity, scalability.
This section checks the basic theoretical foundation of Digital Electronics.
3. Section B – Long Answer / Analytical Questions (30 Marks)
Students must attempt any three (3) questions.
Each question carries 10 marks, requiring detailed explanation, diagrams, and calculations.
This section covers:
● Boolean Expression Simplification
K-map based simplification for a 5-variable function.
● 1:8 Demux using 1:2 Demux
Hierarchical implementation + truth tables.
● Race-Around Condition
Explaining J-K flip-flop issues and Master-Slave solution.
● Sequential Circuit Design (State Diagram)
Creating a flip-flop-based FSM for given cases.
● CMOS & DTL NOR Gate
Design + working explanation in two logic families.
This section tests design skills, logic minimization, and deep understanding of circuits.
4. Section C – Application-Based / Advanced Questions (50 Marks)
This section contains five parts, and students must attempt one question per part.
Each part carries 10 marks, focusing on practical and design-oriented topics.
Part 3 – Gate Realization & Code Conversion
Choice between:
● Implementing Basic Gates Using NAND
Building NOT, AND, OR, XOR, XNOR, NOR using only 2-input NAND.
OR
● Binary to Gray Code Conversion
4-bit code conversion + implementation using EX-OR gates.
Part 4 – Magnitude Comparator / MUX Implementation
Choice between:
● 4-bit Magnitude Comparator
Designing a logic circuit to compare two numbers.
OR
● Boolean Function using 8:1 MUX
Using A, C, D as select lines to realize the given function.
Part 5 – Flip-Flop Conversions / Counter Design
Choice between:
● Converting JK → SR, T, D
Flip-flop conversion with state tables.
OR
● MOD-12 Down Counter
Designing using T flip-flops.
Part 6 – FSM Design
Choice between:
● State Transition Table + Diagram
From given sequential logic expressions.
OR
● 3-bit Synchronous FSM
Count sequence: 0 → 1 → 3 → 7 → 4 → 2 → 0 using D flip-flops.
Part 7 – Logic Families & Memory
Choice between:
● Propagation Delay
Explaining tPHL & tPLH and why tPLH > tPHL.
OR
● ROM Types + 4-T SRAM Cell
Explanation + MOSFET-based implementation.
This section evaluates practical circuit design, state machines, timing concepts, and memory structures.
Final Summary (Purpose of WHAT DESCRIPTION)
This WHAT DESCRIPTION provides a complete, detailed explanation of:
What the question paper contains
What each section asks
How many marks each part carries
What topics students must understand
The overall structure and purpose of the exam
It is a clear, long, section-wise guide to the DIGITAL ELECTRONICS paper.
