Digital Electronics Tutorial

Digital Electronics is a type of electronics that deals with the study of design, working, and applications of systems that operate on digital signals. The systems operating on digital signals are referred to as digital systems and the main constituents of digital systems are digital circuits.

Digital circuits are designed to process data and signals represented in the form of binary numbers, i.e., 0s and 1s. Digital electronics is not limited to the study of digital systems, but it also deals with the analysis of digital signals and development of advanced digital components and technologies.

This comprehensive tutorial on Digital Electronics has been designed for students and professionals who want to learn the concepts of digital electronics. This tutorial covers all the core concepts of digital electronics including number systems, combinational circuits, sequential circuits, IC families, and more.

Introduction to Digital Electronics

We can define Digital Electronics as

"The branch of electrical and electronics engineering that deals with study of design, working, and applications of digital signals and systems."

Digital electronics covers the comprehensive study of digital signals, digital circuits, and digital technologies which are used in electronics, electrical, computers, and communications.

Digital devices and systems are much faster, accurate, reliable, and efficient as compared to analog electronic devices. This is because digital electronic devices are two-state devices and use binary number system to function. Thus, the operation of these devices toggle between only two binary states namely, on (logic 1) and off (logic 0).

A digital circuit or system consists of a large collection of logic gates which are interconnected together to implement a specific Boolean or logic function.

Evolution of Digital Electronics

The following table gives the key milestones in the development of digital electronics and binary logic, from binary number system to modern digital logic gates −

Design and Construction of Digital Circuits

The digital electronic circuits are made up of tiny electronic components called logic gates. Where, logic gates are electronic circuits that can perform a Boolean or logical function on input signals. The main component of logic gates is transistor that acts as a switching device.

An example of digital electronic circuit is shown in the following figure.

Before designing and constructing a digital electronic circuit, designers and engineers try to minimize logic redundancy, so the circuit can become simpler, use fewer components and become cost effective. This also reduces the chances of errors in design and construction of digital circuits. To reduce the logic redundancy, there are various techniques in digital electronics such as Boolean algebra, K-Map, Quine-McCluskey method, etc.

In actual practice, the complex digital circuits are usually implemented using embedded systems and microcontrollers like PLCs, because these systems do not need to be perfectly optimized and can be programmed easily using tools like ladder logic.

Importance of Digital Electronics in Computer Organization

Computer Organization (CO) is a branch of computer engineering that deals with the study of the physical components of a computer system and their functioning. It allows us to understand how different components of a computer system interact with each other to process data, instructions, and perform tasks.

Under computer organization, we study about the hardware architecture and design principles of a computer system. Therefore, computer organization helps computer engineers and system designers to develop more efficient computer systems.

Here are the key points that highlight the importance of Digital Electronics in the field of Computer Organization −

• The binary representation of digital electronics is used to design different circuits of a computer system.
• Digital electronics provide logic gates and other digital circuits which are used in designing different components of a computer system like control units, arithmetic logic units (ALUs), memory unit, and more.
• Digital electronics provide principles for design memory units and data storage systems in computers.
• Digital electronics principles also empower computers to perform various digital signal processing tasks such as modulation, demodulation, filtering, etc.

Digital electronics is the foundational concept in computer organization which provides all the important tools and techniques required for designing and implementing circuits and systems of a computer.

Classification of Digital Electronic Systems

Digital electronic systems are broadly classified into two types namely, combinational systems and sequential systems, and they are −

• Combinational Systems − A digital electronic system that produces an output according to its current inputs only is referred to as a combinational system. It does not remember the past inputs and outputs. Instead, it determines the output immediately based on the present inputs.
• Sequential Systems − A sequential system is a digital electronic system that gives output based on both current inputs and past inputs. In sequential systems, a feedback path and memory element are provided to feed some of the outputs back as inputs.

Sequential systems are further classified into the following two types −

• Synchronous Systems − Those sequential systems that use a clock signal for triggering the change in their state are called synchronous systems.
• Asynchronous Systems − Those sequential systems that do not use any clock signal and change their state according to applied input are called asynchronous systems.

Advantages and Disadvantages of Digital Electronics

The following table highlights some major advantages and disadvantages of digital electronics −

Applications of Digital Electronics

Digital electronics play an important role in every aspect of our lives, from personal devices to advanced industrial systems. In this section, we have highlighted some of the common applications of digital electronics across various fields −

• Computers − Digital electronics is the backbone of computers. In computers, digital electronics allows for storage, processing, and transmission of data and information in digital format.
• Communication Systems − Digital electronics is used in communication systems for information exchange among digital devices like computers, laptops, servers, cell phones, etc. In communication systems, digital electronics provides devices and technologies like modem, multiplexers, encoders, etc. for transmission and reception of digital signals.
• Home Appliances − Digital electronics is also used in various household appliances like smart TVs, music systems, automated washing machines, remote controlled lights, etc.
• Automotives − Digital electronics is being used in modern vehicles for infotainment, engine monitoring and control, navigation, cruise control, etc.
• Industrial Control and Automation − In industries, digital electronics is used for automating and controlling processes like assembly line, manufacturing, etc.
• Medical Devices − Digital electronics is also being used in advanced medical devices like patient monitoring systems, digital x-rays, CT scans, MRI, ECG, etc.

Other applications of digital electronics include military, space research, data processing, simulation, environmental monitoring, security systems, etc.

Important Terms in Digital Electronics

The following terms and their definitions are important and very helpful to grasp the concepts explained in this tutorial −

Binary Number System

It is a number system that uses only two digits, i.e., 0 and 1. Thus, the binary number system is a base 2 number system and acts as the foundational concept in digital electronics. It is used for representing information in digital format as shown below.

Binary Arithmetic

Binary arithmetic is a mathematical method of performing arithmetic operations like addition, subtraction, multiplication, and division on binary numbers. It is the foundation of data processing in digital electronics.

Examples of binary arithmetic are,

$$\mathrm{0 \: + \: 0 \: = \: 0}$$

$$\mathrm{0 \: + \: 1 \: = \: 1}$$

$$\mathrm{1 \: + \: 0 \: = \: 1}$$

$$\mathrm{1 \: + \: 1 \: = \: 0 \: (Carry \: = \: 1)}$$

Boolean Algebra

Boolean algebra is a branch of algebra that deals with the study of logical operations. It was introduced by an English mathematician George Boole. In Boolean algebra, the values of variables can be either true (denoted by 1) or false (denoted 0), and the operators used are logical operators like AND, OR, NOT, etc.

Boolean algebra is used in digital electronics to simplify complex logical functions and optimize the digital circuit designs.

Examples of Boolean algebraic expressions are,

$$\mathrm{A(B+C) \: = \: AB \: + \: AC}$$

$$\mathrm{(\overline{A+B}) \: = \: \bar{A}\:\cdot\:\bar{B}}$$

Logic Gates

Logic gates are the fundamental building blocks in digital electronics. These are the electronic circuits designed to perform Boolean or logical operations.

The common logic gates are AND gate, OR gate, NOT gate, NAND gate, NOR gate, XOR gate, and XNOR gate. Logic gates are important in digital electronics to implement decision making capabilities in electronic circuits.

Combinational Logic Circuits

Combinational logic circuits are the types of digital circuits in which the output depends only on the current inputs. Examples of combinational logic circuits include multiplexers, adders, decoders, etc.

An example of a typical combinational logic circuit is shown in the following figure.

Sequential Logic Circuits

Sequential logic circuits are another type of digital circuits whose output depends on both present and past inputs. These circuits are combinations of combinational circuits and a memory element. Examples of sequential logic circuits include registers, counters, state machines, etc. An example of sequential logic circuit is depicted in the following figure.

Flip-Flops

Flip-flops are nothing but digital circuits that have capability to store 1-bit of data and are used in digital electronics as the basic memory element. There are various types of flip-flops like SR flip-flop, D flip-flop, T flip-flop, JK flip-flop, etc. The following figure shows the circuit diagram of the RS flip-flop.

Multiplexers

Multiplexers are represented as MUX and known as Many-to-One devices. A multiplexer is a digital circuit that select one input from multiple inputs and sent it to the output. The block diagram of a multiplexer is shown below.

Karnaugh Map (K-Map)

K-Map is a graphical tool developed for simplifying complex Boolean expressions. It is used for reducing logic redundancy in digital circuits and make them more design efficient.

K-Map can be used for minimization of logical functions in 2 variables, 3 variables, 4 variables, 5 variables, and 6 variables. For more than 6 variable functions, K-map becomes complex and hard to handle.

Quine-McCluskey Method

It is another method of simplifying or minimizing logical functions to their simplest form. This method was developed to simply complex Boolean expressions using computer systems.

Adders

Digital circuits designed to perform addition of two binary numbers are called adders. Adders are widely used in arithmetic logic units and calculators. There are two types of adders namely, half-adder and full-adder.

A half-adder is an adder circuit that can add only two binary digits and produces a sum and a carry output. While a full-adder is one that can add three binary digits at a time (two input bits and one carry from previous addition) and produces a sum and a carry output.

Shift Registers

Shift registers are digital circuits designed to store multiple data bits and move them in left or right direction depending on control signal.

Counters

Counters are digital circuits designed to count the input pulses and increase or decrease their output accordingly. They are used in digital clocks, timers, and digital control systems.

DAC and ADC Converters

DAC (Digital-to-Analog Converter) are digital circuits that convert digital signals into analog signals and are widely used in devices like amplifiers, audio, video players, etc.

ADC (Analog-to-Digital Converter) are digital circuits that convert analog signals into digital signals and are used in computers, laptops, microcontrollers, and other digital devices.

Programmable Logic Devices (PLDs)

PLDs are digital circuits that can be programmed to perform specific functions in digital systems.

Memory Devices (RAM & ROM)

RAM (Random Access Memory) is a temporary storage device used in digital systems like computers for quick data access during processing. Whereas, ROM (Read Only Memory) is a permanent storage device used to store those programs and instructions that do not need to be changed. Memory devices are important components in digital systems for information storage and retrieval.

Binary Codes

The codes that represent text, numbers, instructions, or any other data using binary digits (0 and 1) are called binary codes. Some common examples of binary codes include BCD, Gray code, ASCII, XS-3, EBCDIC, etc. Binary codes are essential for data storage and processing in digital systems.

Complement Arithmetic

Complements are defined as the pairs of mutually additive inverse numbers. Complement arithmetic is a mathematical method of representing negative numbers and performing subtraction using addition operation. It is mainly used in digital systems like computers to perform subtractions.

Example,

2's Complement = 2^N - Number

Where, N is the number of bits in the number.

The 2's complement of (1001101)₂ will be,

2's Complement = 2⁷ - 1001101

2's Complement = 128 - 1001101

2's Complement = 10000000 - 1001101

2's Complement = 0110011

Who Should Learn Digital Electronics?

This tutorial on Digital Electronics can be suitable for anyone who is interested in learning about digital systems. It is specially designed for beginner students studying electrical, electronics, computer engineering, or any related field at undergraduate or post-graduate level.

It can be also a valuable resource for professionals and practicing engineers in the field of digital electronics, automation and control, communication, etc. It can help them to refresh or deepen their understanding of digital electronics and logic concepts.

Prerequisites to Learn Digital Electronics

This is a most introductory tutorial on Digital Electronics and thus there are not any strict prerequisites. However, if the readers have some familiarity with the fundamental concepts of electronics like current, voltage, circuits, transistors, diodes, resistors, capacitors, etc. then it will help them grasp the concepts covered in this tutorial more easily and effectively.

Additionally, if readers have a basic knowledge of binary numbers and logic gates, then it will make the learning of this tutorial smoother.

FAQs on Digital Electronics

In this section, we have collected a set of Frequently Asked Questions (FAQs) on Digital Electronics followed by their answers −

1. What is meant by digital electronics?

Digital Electronics is a branch of electronics engineering that deals with the study of digital signals and development of devices that can operate on them. Common examples of digital electronics include computers, smartphones, internet, smart TVs, USB drives, etc.

Some of the major reasons why we use digital electronics include the following −

• Digital systems are more accurate and efficient.
• Digital signals and systems are more immune to noise and interference.
• Digital electronic circuits require less power to perform functions.
• Digital systems are easier to design and manufacture, etc.

2. What is digital electronic machine?

Any electronic machine that can perform functions or operations by processing data in discrete form is called a digital electronic machine. These machines use data and instructions expressed in binary codes, i.e., using 0s and 1s. A desktop computer is an example of digital electronic machine.

3. What are the basic gates?

In digital electronics, there are three basic gates namely,

• OR Gate − Takes two or more binary inputs and gives a high (or true) output when any one of the inputs is high.
• AND Gate− Takes two or more binary inputs and gives a high (or true) output when all the applied inputs are high.
• NOT Gate − Takes only one binary input and gives an inverted or complemented output. If input is high, the output will be low and vice-versa.

4. How does Digital Electronics differ from Analog Electronics?

The primary difference between digital and analog electronics is that digital electronics process data in the form of discrete or discontinuous time signals, while analog electronics use continuous signals for processing purposes.

5. Who invented digital electronics?

Digital electronics was not invented by a single person, instead it is a result of research work of many scientists and engineers like George Boole, G. W. Leibniz, Claude Shannon, John Bardeen, W. Brattain, William Shockley, and many other.

6. What is a "clock" in digital electronics?

In digital electronics, a clock is a signal that oscillates between a high and a low state at a constant frequency and used for synchronization of actions in digital circuits.

7. How do Combinational and Sequential Circuits Differ?

A combinational logic circuit is simply an interconnected set of logic gates that produces an output depending on the inputs applied.

On the other hand, a sequential circuit is a group of combinational circuit and memory element. Thus, the output of the sequential circuit is governed by the present inputs and past outputs.

8. What is the Role of Digital Logic Design in Integrated Circuit (IC) Fabrication?

Digital logic design is an important concept in integrated circuit fabrication. It helps the designer in the following processes −

• Determine the specifications and design parameters of the IC.
• Technology mapping, i.e., selection and mapping of logic gates and other components.
• Prepare the physical design and structure to understand the position and interconnection of components.
• Test and verify the design for any error or bug.
• Final product production at mass level.

9. What are FPGAs and Their Role in Digital Electronics?

Field Programmable Gate Arrays (FPGAs) are digital devices in which a matrix of configurable logic blocks (CLBs) is connected together through programmable interconnects.

A user can reprogram an FPGA to meet the needs of a desired application. Therefore, it allows us to design a wide range of custom digital circuits, such as combinational and sequential circuits, arithmetic logic units, memory blocks, control systems, data processing systems, etc.