3.1 DIGITAL ELECTRONICS

### RATIONALE

This course has been designed to make the students know about the fundamental

principles of digital electronics and gain familiarity with the available IC chips. This

subject aims to give a background in the broad field of digital systems design and

microprocessors.

### LEARNING OUTCOMES

After undergoing the subject, student will be able to:

Verify and interpret truth tables for all logic gates.

Realize all logic functions with NAND and NOR gates

Design half adder and full adder circuit

Demonstrate and design 4-bit adder, 2’s complement subtractor

Verify and interpret truth tables for all flip flops.

Verify and interpret truth tables of multiplexer, de-multiplexer, encoder and

decoder ICs

Design a four bit ring counter and verify its operation

Design 4-bit SISO, PISO, SIPO, PIPO shift registers

**DETAILED CONTENTS**

#### 1. Introduction (02 hrs)

a) Distinction between analog and digital signal.

b) Applications and advantages of digital signals.

#### 2. Number System (04 hrs)

a) Binary, octal and hexadecimal number system: conversion from decimal and

hexadecimal to binary and vice-versa.

b) Binary addition, subtraction, multiplication and division including binary

points. Sign magnitude method of representation, 1’s and 2’s complement

method of addition/subtraction, floating point representation

**3. Codes and Parity (04 hrs)**

a) Concept of code, weighted and non-weighted codes, examples of BCD,

excess-3 and Gray code.

b) Concept of parity, single and double parity and error detection and correction

(Hamming code)

c) Alpha numeric codes: ASCII, EBCDIC and Unicode.

#### 4. Logic Gates and Families (07 hrs)

a) Concept of negative and positive logic

b) Definition, symbols and truth tables of gates. Construction of NOT, AND and

OR gates from NAND and NOR gates (universal gates).

(c) Introduction to TTL and CMOS logic families and their sub classification

#### 5. Logic Simplification (06 hrs)

a) Postulates of Boolean algebra, De Morgan’s Theorems. Various identities.

Formulation of truth table and Boolean equation for simple problem.

Implementation of Boolean (logic) equation with gates

b) Karnaugh map (upto 4 variables) and simple application in developing

combinational logic circuits

#### 6. Arithmetic circuits (06 hrs)

a) Half adder and Full adder circuit, design and implementation.

b) Half and Full subtracter circuit, design and implementation.

c) 4 bit adder/subtracter.

d) Adder and Subtractor IC (7484)

e) 2-bit comparator

7. Decoders, Multiplexers and De-Multiplexers (06 hrs)

a) Basic functions and block diagram of Encoders and decoders.

b) Basic functions and block diagram of Multiplexers and De-Multiplexers.

Different types and ICs.

c) Four bit decoder circuits for 7 segment display and decoder/driver ICs.

#### 8. Latches and flip flops (06 hrs)

a) Concept and types of latch with their working and applications

b) Operation using waveforms and truth tables of RS, T, D, JK and Master/Slave

JK flip flops.

c) Difference between a latch and a flip flop

d) Flip flop ICs

#### 9. Shift Register (07 hrs)

Introduction and basic concepts including shift left and shift right.

a) Serial in parallel out, serial in serial out, parallel in serial out, parallel in

parallel out.

b) Universal shift register

c) Buffer register, Tristate Buffer register

d) IC 7495

#### 10. Counters (08 hrs)

a) Introduction to Asynchronous and Synchronous counters

b) Binary up/down counters (upto MOD-8)

c) Decade counter.

d) Pre settable and programmable counters

e) Ring counter with timing diagram

f) Counter ICs

#### 11. Analog to Digital and Digital to Analog Converters (08 hrs)

a) Working principle of A/D and D/A converters

b) Detail study of :

Binary Weighted D/A converter

R/2R ladder D/A converter

a) Brief idea about different techniques of A/D conversion and study of :

Stair step Ramp A/D converter

Dual Slope A/D converter

Successive Approximation A/D Converter

b) Performance characteristics of A/D and D/A converter.

c) Applications of A/D and D/A converter.

**LIST OF PRACTICALS**

1. Verification and interpretation of truth tables for AND, OR, NOT NAND, NOR

and Exclusive OR (EXOR) and Exclusive NOR(EXNOR) gates

2. – Realisation of logic functions with the help of NAND or NOR gates

– Design of a NOR gate latch and verification of its operation

3. – To design a half adder using XOR and NAND gates and verification of its

operation

– Construction of a full adder circuit using XOR and NAND gates and verify its

operation

4. To design 4 bit adder, 2’s complement subtractor circuit using an 4 bit adder IC

and an XOR IC and verify the operation of the circuit.

5. To design a NOR Gate Latch and verification of its operation

6 Verification of truth table for positive edge triggered, negative edge triggered,

level triggered IC flip-flops (At least one IC each of D latch , D flip-flop, JK flipflops).

7. Verification of truth table for encoder and decoder ICs, Mux and DeMux

8. To design a 4 bit SISO, SIPO, PISO, PIPO shift registers using JK/D flip flops and

verification of their operation.

9. To design a 4 bit ring counter and verify its operation.

10. Asynchronous Counter ICs

Verification of truth table for any one universal shift register IC

Use of IC 7490 or equivalent TTL (a) divide by 2 (b) divide by 10 Counter

OR

Use of IC 7493 or equivalent TTL (a) divide by 2 (b) divide by 8 (c) divide by

16 counter

Note: Above experiments may preferably be done on Bread Boards.

**INSTRUCTIONAL STRATEGY**

The digital systems in microprocessors have significant importance in the area of

electronics. Adequate competency needs to be developed by giving sufficient practical

knowledge in microprocessors (programming as well as interfacing), A/D, D/A

Converters and other topics. Help may be taken in the form of charts, simulation packages

to develop clear concepts of the subject. Programming exercises other than the tested in

circulation may be given to the students.

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### RECOMMENDED BOOKS

1. Digital Electronics and Applications by Malvino Leach, Tata McGraw Hill Education Pvt Ltd, New Delhi

2. Digital Logic Designs by Morris Mano, Prentice Hall of India,New Delhi

3. Digital Circuits and Design by DP Kothari and JS Dhillon, Pearson Publication, New Delhi

4. Digital Electronics by Soumitra Kumar Mandal, Tata McGraw Hill Education Pvt Ltd.

5. Digital Electronics by Tokheim, Tata McGraw Hill Education Pvt Ltd.

6. Digital Fundamentals by Thomas Floyds, Universal Book Stall

7. Digital Electronics by RP Jain, Tata McGraw Hill Education Pvt Ltd, New Delhi

8. Digital Electronics by KS Jamwal, Dhanpat Rai and Co., New Delhi

9. Digital Electronics by BR Gupta, Dhanpat Rai & Co., New Delhi

10. Digital Systems: Principles and Applications by RJ Tocci, Prentice Hall of India, New Delhi

11. Digital Electronics by Rajaraman V., Prentice Hall of India, New Delhi

### INTRODUCTION TO DIGTAL ELECTRONICS

##### Download Previous Year Digital Electronics 3rd Sem Semester Question Paper Solution Click Here

### 2.NUMBER SYSTEM

What is Zener diode? Draw its symbol and characteristics

hybrid Parameter) of transistor

Temperature variations affect the operating point of a transistor

Phase reversal of output voltage with respect to input voltage in an Amplifier

#### Basic Electronics PSBTE Diploma Solved Paper May 2017 Solution Click Here

### Section c solved bee paper

CE configuration of a Transistor Click Here