We live in an analog world. There are an infinite amount of colors lớn paint an object (even if the difference is indiscernible khổng lồ our eye), there are an infinite number of tones we can hear, and there are an infinite number of smells we can smell. The common theme among all of these analog signals is their infinite possibilities.

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Digital signals và objects deal in the realm of the discrete or finite, meaning there is a limited phối of values they can be. That could mean just two total possible values, 255, 4,294,967,296, or anything as long as it"s not ∞ (infinity).


Real-world objects can display data, gather inputs by either analog or digital means. (From left khổng lồ right): Clocks, multimeters, & joysticks can all take either khung (analog above, digital below).

Working with electronics means dealing with both analog và digital signals, inputs and outputs. Our electronics projects have to lớn interact with the real, analog world in some way, but most of our microprocessors, computers, and xúc tích và ngắn gọn units are purely digital components. These two types of signals are like different electronic languages; some electronics components are bi-lingual, others can only understand & speak one of the two.

In this tutorial, we"ll cover the basics of both digital & analog signals, including examples of each. We"ll also talk about analog and digital circuits, and components.


Suggested Reading

The concepts of analog and digital stand on their own, & don"t require a lot of previous electronics knowledge. That said, if you haven"t already, you should peek through some of these tutorials:

And some mathematics concepts: reading graphs, and understanding the difference between finite & infinite sets.

Analog Signals

Define: Signals

Before going too much further, we should talk a bit about what a signal actually is, electronic signals specifically (as opposed lớn traffic signals, albums by the ultimate power-trio, or a general means for communication). The signals we"re talking about are time-varying "quantities" which convey some sort of information. In electrical engineering the quantity that"s time-varying is usually voltage (if not that, then usually current). So when we talk about signals, just think of them as a voltage that"s changing over time.

Signals are passed between devices in order khổng lồ send and receive information, which might be video, audio, or some sort of encoded data. Usually the signals are transmitted through wires, but they could also pass through the air via radio frequency (RF) waves. Audio signals, for example might be transferred between your computer"s audio card and speakers, while data signals might be passed through the air between a tablet and a WiFi router.

Analog Signal Graphs

Because a signal varies over time, it"s helpful khổng lồ plot it on a graph where time is plotted on the horizontal, x-axis, và voltage on the vertical, y-axis. Looking at a graph of a signal is usually the easiest way to identify if it"s analog or digital; a time-versus-voltage graph of an analog signal should be smoothcontinuous.

While these signals may be limited lớn a range of maximum và minimum values, there are still an infinite number of possible values within that range. For example, the analog voltage coming out of your wall socket might be clamped between -120V and +120V, but, as you increase the resolution more và more, you discover an infinite number of values that the signal can actually be (like 64.4V, 64.42V, 64.424V, và infinite, increasingly precise values).

Example Analog Signals

Video & audio transmissions are often transferred or recorded using analog signals. The composite video clip coming out of an old RCA jack, for example, is a coded analog signal usually ranging between 0 and 1.073V. Tiny changes in the signal have a huge effect on the màu sắc or location of the video.

Pure audio signals are also analog. The signal that comes out of a microphone is full of analog frequencies và harmonics, which combine khổng lồ make beautiful music.

Digital Signals

Digital signals must have a finite mix of possible values. The number of values in the mix can be anywhere between two và a-very-large-number-that"s-not-infinity. Most commonly digital signals will be one of two values -- like either 0V or 5V. Timing graphs of these signals look lượt thích square waves.


Or a digital signal might be a discrete representation of an analog waveform. Viewed from afar, the wave function below may seem smooth và analog, but when you look closely there are tiny discrete steps as the signal tries lớn approximate values:

That"s the big difference between analog and digital waves. Analog waves are smooth & continuous, digital waves are stepping, square, và discrete.

Example Digital Signals

Not all audio and video clip signals are analog. Standardized signals lượt thích HDMI for clip (and audio) & MIDI, I2S, or AC"97 for audio are all digitally transmitted.

Most communication between integrated circuits is digital. Interfaces like serial, I2C, và SPI all transmit data via a coded sequence of square waves.

Analog và Digital Circuits

Analog Electronics

Most of the fundamental electronic components -- resistors, capacitors, inductors, diodes, transistors, và operational amplifiers -- are all inherently analog. Circuits built with a combination of solely these components are usually analog.

Analog circuits are usually complex combinations of op amps, resistors, caps, & other foundational electronic components. This is an example of a class B analog audio amplifier.

Analog circuits can be very elegant designs with many components, or they can be very simple, like two resistors combining lớn make a voltage divider. In general, though, analog circuits are much more difficult khổng lồ design than those which accomplish the same task digitally. It takes a special kind of analog circuit wizard khổng lồ design an analog radio receiver, or an analog battery charger; digital components exist lớn make those designs much simpler.

Analog circuits are usually much more susceptible to lớn noise (small, undesired variations in voltage). Small changes in the voltage màn chơi of an analog signal may produce significant errors when being processed.

Digital Electronics

Digital circuits operate using digital, discrete signals. These circuits are usually made of a combination of transistors and súc tích gates and, at higher levels, microcontrollers or other computing chips. Most processors, whether they"re big beefy processors in your computer, or tiny little microcontrollers, operate in the digital realm.

Digital circuits make use of components lượt thích logic gates, or more complicated digital ICs (usually represented by rectangles with labeled pins extending from them).

Digital circuits usually use a binary scheme for digital signaling. These systems assign two different voltages as two different ngắn gọn xúc tích levels -- a high voltage (usually 5V, 3.3V, or 1.8V) represents one value và a low voltage (usually 0V) represents the other.

Although digital circuits are generally easier khổng lồ design, they bởi tend khổng lồ be a bit more expensive than an equally tasked analog circuit.

Analog và Digital Combined

It"s not rare khổng lồ see a mixture of analog and digital components in a circuit. Although microcontrollers are usually digital beasts, they often have internal circuitry which enables them to lớn interface with analog circuitry (analog-to-digital converters, pulse-width modulation, & digital-to-analog converters. An analog-to-digital converter (ADC) allows a microcontroller khổng lồ connect lớn an analog sensor (like photocells or temperature sensors), lớn read in an analog voltage. The less common digital-to-analog converter allows a microcontroller to lớn produce analog voltages, which is handy when it needs khổng lồ make sound.

Resources và Going Further

Now that you know the difference between analog & digital signals, we"d suggest checking out the Analog khổng lồ Digital Conversion tutorial. Working with microcontrollers, or really any logic-based electronics, means working in the digital realm most of the time. If you want khổng lồ sense light, temperature, or interface a microcontroller with a variety of other analog sensors, you"ll need to lớn know how to lớn convert the analog voltage they produce into a digital value.

Interested in trabzondanbak.coming more foundational topics?

See our Engineering Essentials page for a full list of cornerstone topics surrounding electrical engineering.

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Also, consider reading our Pulse Width Modulation (PWM) tutorial. PWM is a trick microcontrollers can use to lớn make a digital signal appear to lớn be analog.

Here are some other subjects which giảm giá heavily with digital interfaces:

Or, if you"d like to delve further into the analog realm, consider checking out these tutorials: