(SEM IV) THEORY EXAMINATION 2024-25 DIGITAL ELECTRONICS

The uploaded document is the B.Tech Semester IV Theory Examination Paper (2024–25) for the subject BOE410 – Digital Electronics. This is an official university exam paper designed to thoroughly assess a student’s knowledge of number systems, combinational circuits, sequential circuits, Boolean algebra, memory devices, logic families, and the fundamentals of digital system design. The examination carries 70 marks and must be completed within 3 hours. The paper is bilingual — English and Hindi — ensuring that students from different language backgrounds can understand the questions clearly.
 

BOE410-DIGITAL-ELECTRONICS

The exam begins with Section A, which contains seven compulsory short-answer questions, each carrying 2 marks. These questions test the student’s basic conceptual understanding of digital electronics. They include converting hexadecimal to binary, explaining the concepts of 1’s and 2’s complement, understanding the role of a decoder in digital circuits, and defining the characteristic equation of a flip-flop. Students must also describe the importance of state reduction in sequential circuit design, mention differences between PLA and PAL, and explain the meaning of fan-in and fan-out in logic families. Although brief, these questions ensure that the student has a solid foundation in the essential building blocks of digital logic.

Section B shifts toward deeper descriptive questions. Students must attempt any three out of five questions, each worth 7 marks. These questions require students to explain SOP and POS forms with examples, design a 4:1 multiplexer using basic logic gates, and draw and explain the block diagram of a synchronous decade counter. The section further explores the steps involved in designing asynchronous sequential circuits, which require special attention due to hazards, races, and unstable states. Additionally, students must compare TTL and CMOS logic families based on power consumption and speed, demonstrating their understanding of how different technologies influence digital system performance. This section tests conceptual depth, design ability, and the student’s capacity to represent logic circuits clearly.

The exam concludes with Section C, which contains long analytical questions divided into multiple parts. In each subsection (Q3 to Q7), the student must choose and attempt one question. These questions are more advanced and require detailed reasoning, step-by-step calculations, and often diagrammatic representation. For example, students may be asked to explain Gray Code, convert binary to Gray Code, and describe its practical significance in reducing errors during digital transitions. Another question uses a Karnaugh Map (K-map) to simplify a Boolean expression and then requires the student to implement the simplified expression using NOR gates only, testing both minimization techniques and gate-level implementation.

Further questions include designing a 2-bit magnitude comparator, which requires a clear understanding of combinational circuit design, or constructing a full adder using two half adders and an OR gate, emphasizing modular design. Sequential circuit questions include explaining the JK flip-flop using its logic diagram and characteristic table, along with drawing and explaining the working of a bidirectional shift register. More advanced topics include hazards in asynchronous circuits and how race conditions can be prevented. Students may also be required to explain the role of flow tables in designing asynchronous sequential circuits, showcasing their understanding of unstable and stable states.

The final part of Section C focuses on memory and logic families. Students may be asked to explain the internal structure and implementation method of ROM for a three-variable Boolean function, demonstrating practical memory design skills. Another option is writing a detailed note on the CMOS logic family, including its benefits over TTL technology such as low power consumption and higher noise immunity. These questions ensure the student understands both theoretical and practical aspects of digital system design.

Overall, the paper provides a complete and well-balanced assessment of the subject Digital Electronics. It ensures that students are tested on basic concepts, design principles, analytical techniques, circuit implementation skills, and advanced digital system behavior. With bilingual formatting, a mix of short and long questions, and deep coverage of both combinational and sequential logic, this exam paper serves as a comprehensive tool for evaluating the student’s mastery of digital electronics.