## 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
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
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)

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

### 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

## DIGITAL ELECTRONICS DIPLOMA PAPER SOLUTION

### 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