A Guide to Understanding Analog Signals and Inputs

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The world we live in is analog. The number of colors people can use to paint something is infinite, the number of smells they can smell is infinite, and the number of stars in the sky is infinite. All analog signals have one common theme – their infinite possibilities.

On the other hand, digital signals are finite and discrete which means that there is a limit to the values these signals can have. When working with electronics, you have to deal with both digital and analog signals and analog and digital inputs and outputs. In this post, we will help you understand what analog signals and inputs and how they are different from digital signals and inputs.

Analog Signals

Analog signals are time-varying quantities which convey some kind of information. These signals are passed between devices to send information and receive it. Usually, analog signals are transmitted from one destination to another through wires. However, they can also pass through the air via radio waves. Audio signals that pass between the audio card of your computer and speakers are one example of analog signals.

A time versus voltage graph of analog signals is continuous and smooth. While these signals can be limited to a range of minimum and maximum values, within that range an infinite number of values can exist. For example, the analog voltage that comes out of the wall socket might be in the range of-110V and +110V. However, if you increase the resolution, you will see that there are infinite values in the signal, like 54.5V, 54.56V, 55.4V, etc.

Analog Input

Analog input is the analog signal that is transmitted into a device (sensor) to provide information or to be processed and converted into a digital signal.

Example of Analog Signals

Audio and video transmissions are usually transferred and recorded through analog signals. For example, the composite video that comes out of an RCA jack is an analog signal often ranging between 0V and 1.073V. Audio signals are mostly analog too. For example, the signal that microphone generate is made up of analog frequencies which combine with harmonics to create music.

Digital Signals

All digital signals have a finite number of possible values. These signals usually have two values – 0V or 5V. The time graphs of digital signals look similar to square waves. Digital signals can be discrete representations of analog waveforms. When you view it from far, the discrete digital signal may look smooth. However, when you look at the signal up close, you will see tiny discrete steps. That is the major difference between digital and analog signals. The waves of analog signals are continuous and smooth while digital waves are square, stepping, and discrete.

Example of Digital Signals

Not all video and audio signals are analog. MIDI, HDMI, and other standardized signals for audio and video are digitally transmitted. Moreover, the communication that takes place between integrated circuits is mostly digital. Interfaces like SPI and serial also transmit digital data.

Analog to Digital

In order to input an external analog signal into a computer, there must be an infinite number of digital values to represent the converted digital quantity. This isn’t possible since a computer system can only handle a finite number of digits.

This problem is solved by keeping the number of digits in the computer system within a certain acceptable range by using either the ceiling or floor or by rounding. In simple words, the analog value is replaced with a digital value within a certain range. This is called quantization.

When analog values are quantized, the solid line representing analog input is replaced by a stepped line. This lets you express analog signals using finite values. Quantization principle is applied in a number of devices. For example, in mobile phones, voices (analog) signals are transferred into digital signals that are received by the device and then transferred to the other device before again being converted into an analog signal (voice).

Analog Electronics

The majority of the basic electronic components like capacitors, resistors, diodes, inductors, operational amplifiers, and transistors are analog by nature. Circuits that are built using a combination of these components only are usually analog.

Analog circuits are elegantly designed and usually have many components. However, they can be simple too like combining two resistors to create a voltage divider. Generally designing analog circuits is harder than building digital ones. One downside of analog circuits is that they are very susceptible to noise. Noise can create changes in the analog signal’s voltage level which can lead to significant errors during processing. This is why digital signals are preferred over their analog counterparts.

Digital Circuits

Digital circuits use discrete, digital signals to operate. These are made of different combinations of logic gates and transistors. More complex digital circuits involve microcontrollers or other chipsets. Most processors including the silicon chip in your computer system or the tiny microcontrollers like Arduino involve the use of digital circuits.

A binary scheme is used by digital circuits for digital signals. Two different voltages – a high voltage and a low voltage – are assigned by these systems as two logic levels.  The high voltage represents one value while the low voltage represents the other.

Digital circuits are easier to design but they tend to be more expensive.

Digital and Analog Combined

Some circuits are made up of a combination of digital and analog components. For example, a microcontroller has several digital components, but it also includes analog circuitry which allows it to interface with analog input. The analog-to-digital converter of a microcontroller allows it to read analog input and process it.

Final Thoughts

We have shown you some of the most important things about analog signals, inputs, and circuits. We have also discussed how they are different from digital signals, inputs, and circuits. If you want more information about analog inputs and hardware that can process analog signals and inputs, visit this helpful page.

Since we’re living in the digital age, understanding key terms like the above is vital.