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Digital Logic Design: Combinational Logic

Mark A. Strain, PE


Course Outline

Digital circuits have been incorporated into everyday life. Life would definitely be different without their existence. Digital logic is the fundamental basics of computer design. This course will explain some of the fundamental building blocks of logic design.

This course is intended to be a review of the basics of digital logic starting with the binary numbering system, hexadecimal numbering system, logic gates, and logic circuits. This course will go over the basic logic gates, adders, decoders, encoders, multiplexers, and demultiplexers. This course has a lot of sample problems and teaches by showing examples.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course the student will learn:

Intended Audience

This course is intended for all engineers.

Benefit to Attendees

Attendee of this course will be able to understand the basics of microcontrollers and microprocessors.

Course Introduction

You will encounter digital circuits multiple times in any given day. Digital circuits have infiltrated society in ways unheard of only a few decades ago. They are everywhere and seem to be in everything. Without them we would have no microprocessors. Without microprocessors we would have no computers or smartphones or sophisticated fifth-generation fighter jets or even something as simple and convenient as a coffee maker that brews the coffee before we wake up that shuts off automatically when we forget to turn it off. Maybe we could still design a coffee maker with an analog clock with a mechanical switch that will shut off the hot plate when the clock advances forward past a mechanical set point, but the point is that these little devices (digital circuits) are commonplace and here to stay.

Digital circuits are comprised of tiny little on/off switches called transistors. The transistor is the building block of all digital circuits. This revolutionary little switching device was invented in 1947 and its creators were awarded the Nobel Prize in Physics a few years later, and rightly so. Only a few other inventions have impacted and affected our lives in so many ways.

The transistor is the fundamental building block of digital circuits. It has been miniaturized by many orders of magnitude since its inception. This has allowed for the explosive growth in the complexity of digital circuits and microprocessors. Before the transistor computers were built with mechanical switches called relays. There were bulky, slow and highly prone to failure. If the computing industry was limited to using mechanical relays for processor cores, then the progression in computing technology would have come to a halt decades ago. Simple "hand" calculators would still be the size of a room and we would have no mobile phones not to mention a smartphone that understands the spoken language, "Siri, send a text".

Transistors can be organized into logic gates. The most basic gates are AND, OR and NOT. With these fundamental gates, all other gates can be built. Boolean algebra describes logic gates in symbolic form which gives a designer the ability to design a complicated logic circuit using math by forming equations. These equations are directly transformed into logic symbols and into a logic circuit. Connecting several logic gates together forms something called combinational logic. With this combinational logic, adders can be fabricated as well as encoders, decoders, multiplexers and demultiplexers. A multiplexer is a device that allows one input to be selected from several inputs. An arithmetic logic unit (ALU) is a multiplexer which is at the heart of a microprocessor's core.

Course Content

This course is in the following PDF document:

Digital Logic Design: Combinational Logic

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

Digital circuits have infiltrated every part of modern society. Life would definitely be different without their existence. The transistor is the fundamental building block in all digital circuits. Its miniaturization has allowed for the explosive growth in the complexity of digital circuits and in computing power. Transistors are organized into logic gates, the most basic being the AND, OR and NOT gates. With these fundamental gates, all other gates are built. Combinational logic is formed when several gates are connected together to form a more complicated circuit. With this combinational logic, adders can be built as well as encoders, decoders, multiplexers and demultiplexers.  

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.