Digital Circuits Overview for Electrical Engineers: What You Need to Know

December 15, 2020

View all blog posts under Articles | View all blog posts under Online Master of Science In Electrical Engineering

An electrical engineer studies a circuit diagram. Human perception is based on how we interpret analog information. For example, the brain processes sound and light waves into the sounds we hear and the sights we see. That analog information can be digitized — transformed into bits that computers and devices can process — for storage and transmission, then turned back into a signal that we can see, hear, and understand.

Powering this constant transformation are two types of electric circuits.

Analog circuits continuously transmit information that the human brain processes.
Digital circuits discontinuously transmit information in zeros and ones that computers and machines

Both analog and digital data moves via signals (i.e., electromagnetic or electrical currents that carry data from one device or component to another). However, the two types of circuits deliver data differently.

Analog circuits deliver data through signals via amplitude and frequency.
Digital circuits transmit data through pulses using the binary system: ones and zeros. In electrical design, one bit represents high voltage, while zero bits represent low or no voltage.

Digital circuits are fundamental to making devices that power our daily lives. They provide the building blocks of technology and electronics that enable us to listen to our favorite music, keep in touch with loved ones, and more.

Individuals who are pursuing an advanced career in electrical engineering should understand the language, technology, components, and characteristics of both analog and digital circuits. This knowledge is essential for developing innovative electronics and technology systems in a cost-efficient manner.

A graduate degree in electrical engineering, such as an online Master of Science in Electronic Engineering, can prepare individuals with advanced knowledge of digital circuit design and the essential technical skills to help drive global change.

Analog vs. Digital Circuits: A Comparative Overview

A comparison of analog vs. digital circuits reveals variances in their design and differences in how they transmit data.

Analog Circuits

Analog signals provide a continuous output of information with a wide range of possible values. They exist in various natural physical forms: light waves and sound waves, for example. Analog signals can be detected and analyzed using instruments such as oscilloscopes, voltmeters, and recording devices.

Before the advent of computer and digital technology, devices such as radios, televisions, and telephones used analog signals to transmit information such as music, images, and voice. Typical applications included record players, landline telephones, photocopiers, and video recorders, to name a few. Many of these technologies have undergone digital transformations — think digital music streaming services, smartphones, and satellite radio.

Analog circuits remain in use today in various applications including temperature sensors, FM radio signals, and audio and visual equipment.

Characteristics of analog circuits include the following.

The traditional building blocks of analog circuits involve electronic components such as resistors, capacitors, diodes, transistors, and amplifiers. These parts work in connection to gather and transmit continuous voltage signals within a specified area.
Analog circuits work with a continuous range of values that represent various types of information. However, analog waves are susceptible to noise, which means they may inadvertently distort signals. Noise, which can be described as unwanted voltage variations during signal transmissions, can weaken and degrade signal strength, resulting in output errors.
Analog signals travel as smooth and continuous waves. To analyze analog signals using computers, those waves must be converted into digital signals that are denoted by square or stepped waves.
Analog circuits can range from very complex to simple. Still, they typically offer electrical engineers a lack of design flexibility.

Digital Circuits

While analog circuits can directly transmit signals, a digital circuit must first alter the analog signal to interpret it. Then, it changes the information back to an analog signal that humans can understand.

Digital circuit designs consist of transistors and logic gates that execute a Boolean logic operation, determining that values are true or false. The binary system quantifies values as either 1 or 0, which can also mean that a value is “on” or “off.” Digital electronic devices and computer processors use a binary methodology to analyze and interpret information. They also use it to perform desired functions and output data in analog form so humans can understand it.

Digital circuit characteristics include the following.

Binary systems and electronic design automation (EDA) tools and software enable electrical engineers to use digital circuits to efficiently design technology and electronics.
Digital circuits allow for data transmission, storage, and retrieval without the noise associated with analog circuits. This reduces data degradation.
Changes, corrections, or added functionality do not require costly hardware updates, thanks to software that can provide remote circuit manipulation.
Digital circuits consist of Boolean algebra and logic gates, which are inexpensive. Configuring digital signals is also more straightforward than configuring analog ones.

Today’s technology makes use of both analog and digital circuitry. Some electrical engineers work with large-scale electrical systems such as utility and power generation plants. This may include designing motor controls for various applications that use both analog and digital circuits.

Electrical engineers may also work on developing household appliances, lighting and telecommunication systems, and satellite communications. In each of these areas, electrical engineers need a thorough understanding of the differences between analog circuits and digital circuits to build the most efficient and integrated device or system possible.

What Are Digital Integrated Circuits?

Integrated digital circuits are another type of digital circuit. They are foundational components in electronics and technology equipment such as radios, smartphones, televisions, game consoles, navigation systems, and satellite systems.

An integrated circuit in general is an electronic device that assembles various electronic components on a small semiconductor chip. Devices, such as transistors and their interconnected elements, are integrated on semiconductor material, typically silicon, at small scale. Silicon is a readily available material found in sand. The components are generally microscopic in size.

Integrated circuits are typically designed with specific functionalities. For example, an integrated circuit can be designed for the sole purpose of amplifying a signal’s voltage. This can streamline the design process, saving electrical engineers valuable time in developing components for a new technology product.

Integrated circuits can be either analog or digital. Integrated analog circuits typically handle continuous signals, such as sound, and are commonly used for audio and visual applications. For example, when a band plays music on stage, they produce analog signals known as sound waves. In a venue such as a stadium, people furthest away from the band might not hear the music without amplification. Enter the microphone, a device with an analog circuit that detects, modifies, and amplifies the sound signal and feeds it to a loudspeaker. The analog circuit reproduces the sounds initially detected by the microphone.

On the other hand, digital integrated circuits handle discrete signals. They consist of many more transistors compared to analog integrated circuits. Digital integrated circuits execute specific system functions using the binary number system and the logic of Boolean algebra.

The binary number system is a mathematical system that uses only two different digits: 0 and 1. This contrasts with the decimal system, which includes 10 different symbols. The list below shows the number in the decimal system and its corresponding binary value.

0 = 0
1 = 1
2 = 10
3 = 11
4 = 100
5 = 101
6 = 110
7 = 111
8 = 1000
9 = 1001
10 = 1010

The 1s and 0s of the binary system represent two states, represented in values as either on-off or open-closed. Similarly, Boolean algebra represents two values: true and false. Boolean algebra is a foundational aspect of integrated digital circuit design.

Digital integrated circuits use Boolean logic and operate through logic gates, which are physical arrangements of interconnected transistors in a digital chip that are invisible to the naked eye. Logic gates, which work with binary data, include three basic operations AND, OR, and NOT. These operations can be combined to form additional operational combinations: NAND (NOT AND) and NOT (NOT OR). By combining these logic gates, an electrical engineer can design a series of logic gates to create a complex integrated circuit for many applications.

Exploring VHDL Language

The world of digital circuits has a distinct language; terms like binary and Boolean are just the beginning. Another critical term is VHDL.

The “V” in the acronym stands for VHSIC or Very High-Speed Integrated Circuit. VHSIC describes a fast processor. The abbreviation was also the name of a 1980s U.S. government program that focused on researching and developing high-speed computer chips.
“HDL” stands for Hardware Description Language. HDL is comparable to the programming languages used in software, except that its purpose is to design computer chips.

VHDL language is essential to the circuit design process, specifically for developing models.

VHDL model approaches include behavioral modeling and structural modeling.

The behavioral model describes the input and output response of a component.
The structural model describes the interconnection and wiring of components in an integrated circuit, or how the building blocks are put together to build a circuit. The result is an accurate description of where to put which components and wires.

Engineers who design circuits may work with large systems such as power grids, or at the small-scale individual transistor level. While a simple circuit design can be a one-person job, complex systems may require teams of electrical engineers. VHDL language enables electrical engineers to define the behavior of digital logic and develop high-level models for integrated circuits. It can also be used to design hardware and create test entities to verify that hardware’s behavior.

Circuit design involves the use of computer simulations to determine the most efficient process of transmitting data from one apparatus to another. VHDL language can be used to simulate and test the circuit functionality in achieving this goal. The simulations’ results, including outcomes from testing the design, inform electrical engineers on the physical constructs of an electronic circuit.

A synthesis tool runs the code to create and optimize a circuit design. Moving the circuit design process from conception to manufacturing requires developing blueprints that describe the size, shape, interconnections, and other information about the circuit.

A Look at VLSI Technology

The development of complex semiconductor and communication technologies in the 1970s led to Very Large Scale Integration (VLSI) technology. VLSI describes the process of using thousands of different transistors to build an integrated circuit, such as a microchip.

Before VLSIs, integrated circuits were limited in their functionality. Components such as the CPU, ROM, RAM, and other computer peripherals took up a lot of space, limiting the ability to scale up functionality. VLSI is a process that enables integrated digital circuit designers to include critical components on a single chip.

VLSI technology makes it possible for designers to increase the functional density of digital circuits. This makes it easier to develop robust applications that occupy a much smaller area. Industries such as the electronics, automotive, and medical fields take advantage of VLSI to create advanced technological innovations.

For example, electrical engineers can design integrated digital circuits that make handling life-saving medical devices more manageable and less awkward to use. In addition to implantable devices, digital circuits have made it possible to miniaturize imaging and surgical instruments, such as handheld and mobile imaging systems and surgical robotics. Consider micro-scale cameras that can be swallowed by patients, which can take images of the gastrointestinal tract in a less invasive way than traditional endoscopes.

Additional efficiency-related benefits of VLSI technology include the following.

Reduced size: Making devices and equipment more manageable
Lower power requirements: Improves power consumption and efficiency
Improved cost-effectiveness: Delivers more functionality at a lower cost
Improved performance: Faster and more reliable performance

Building a Vital Connection

While the world undergoes a digital transformation, one thing will remain constant: humans continue to perceive the world in analog. We understand analog signals, which can come in the form of the sounds we hear and the images we see. On the other hand, computers are digital. Information understood by computers comes in the form of digital bits. This form of signal enables computers to process and store data more efficiently than ever thought possible.

We increasingly rely on computers to access the data that powers and improves our modern lives. Still, humans need the information to be presented in analog to understand it. Digital circuits move data from the analog world to the digital world and back — enabling humans to perceive, enjoy, learn, and understand the information.

Electrical engineers develop the circuits that make this remarkable communication between humans and computers possible.

From radios and mobile phones to autonomous unmanned vehicles…from electronic navigation systems to micro-nano devices and far beyond — electrical engineers play a pivotal role in developing innovative technologies that move the world forward.

Students who want to understand engineering systems at an advanced level, and who wish to engineer a better future with responsible and sustainable design, should learn more about Ohio University ’s online Master of Science in Electronic Engineering. The program offers the knowledge and skill to research, design, develop, and test new technologies and industry applications that can help make an impact on the world around us.

Embark on a new career at the forefront of technology with Ohio University.