Digital Input vs. Analog Input: What’s the Difference?

The following guides compare digital input vs. analog input. You must understand the differences between these two technologies.

Especially if you plan to work with microcontrollers, single-board computers (SBCs) and Programmable Logic controllers (PLCs).

You may have noticed that these technologies have labels indicating that they accept digital or analog input.

But what’s the difference? This guide will answer this question and more. 

Table of Contents

What Are Input Signals?

Signals allow different devices to interface and communicate.

For this to happen, they must be able to exchange information or data.

Ultimately, signals serve as electric conduits to transport this information.

Digital and Analog input refers to the type of signals a device or port accepts.

Typically, an output device sends an outgoing signal to an input device. 

Microcontroller circuit diagram with input pins

Microcontroller circuit diagram with input pins

What are Digital Input Signals?

Digital input signals carry an inconsistent flow of discrete data. Typically, they’re halting and non-consistent.

For instance, a digital signal with binary values can have either one (high-level) or zero (low-level).

Thus, square waves typically represent the structure of these types of input signals.

Digital Input Signal  

Digital Input Signal  

They are the most widespread type of input for modern PLCs.

This is because they have high bandwidths, making them ideal for computing.

They’re also resistant to noise which makes them highly accurate.     

What are Analog Input Signals

Analog input signals carry consistent or continuous waves of data. Thus, they are often represented by sine waves:

Sine Waves 

Sine Waves 

The most common forms of analog input signals include (but are not limited to) temperature, voltage, and current.     

General Purpose Input/Output

You may have noticed that some microcontrollers and SBCs have General Purpose Input Output pins.

As the name suggests, these devices can use these pins to either receive signals (input) or send signals (output).

Software on the device controls whether it outputs or accepts signals. 

Moreover, these devices come with analog-to-digital converters (ADC) that can convert analog input signals into digital signals.

Often, this is how values from pressure and temperature sensors become represented as digital ones.  

SBC/Controller that administers multiple sensors 

SBC/Controller that administers multiple sensors 

Digital Input vs. Analog Input: Comparison Table

The following table summarizes the differences between digital and analog input signals. 

AttributeDigital InputAnalog Input
SignalDigital input signals use discrete values that are often in the form of binary values.Analog inputs use a continuous signal. 
Physical RepresentationWe usually represent digital inputs as a square wave.Analog inputs usually come in the form of sine waves. However, on rare occasions, they may also present themselves as triangle waves. 
Bandwidth RequirementsDigital input signals usually require higher bandwidth when compared to analog signals.  Analog inputs require lower bandwidth when compared to digital inputs. It’s one of the few advantages analog input has over digital input.  
Suitable ApplicationsIdeal for communications between computational machines and digital electronics.Analog input signals are ideal for media applications and sensor information. This includes audio, video and various forms of measurement data.
Susceptibility to Electronic NoiseDigital input signals are highly resistant to electronic noise. This makes them more reliable and accurate than analog input signals.Analog signals are highly susceptible to electronic noise. PCBs and circuits can experience sudden changes (such as spikes or dips) in current. This causes noise. In such circumstances, analog signals can be disrupted, rendering them inaccurate.
Power ConsumptionBecause digital inputs do not transmit in a single continuous stream, they’re more power efficient than analog input signals.  Analog signals transmit in a single continuous stream. Thus, they have relatively high power consumption. 
Circuit ComponentsDigital input signals are used and processed by (mostly active) components such as logic gates, transistors and digital integrated circuits. Analog input signals are processed by passive components including resistors and capacitors.
Use CasesIn computer peripherals such as keyboards. They send digital signals to and from your computer in a stream of binary numbers.Electric fans, sensors and volume controls for radios are some of the most widespread uses for analog signals. 

Conclusion

Analog vs Digital Signals

Analog vs. Digital Signals

The above guide examines digital input vs. analog input signals. Suffice it to say that these signals differ in their purposes and usages. Technically, no signal is better than the other.

Although digital signals are far more power-efficient, accurate and reliable, analog input signals still have their place worldwide.

For instance, we can still use it to carry video and audio data.

Furthermore, many devices come with analog-to-digital converters and even digital-to-analog converters.

Nevertheless, if you want to learn more about PCB-related technology such as these, don’t hesitate to contact us or visit the rest of our website.  

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Emma Lu
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