Why Do We Need Analog to Digital Convertors?

January 31, 2018

In the world of digital signal processing, the importance of analog to digital conversion can never be understated. These devices play an important role in simplifying signal processing by making things easier for engineers and analysts.

But have you ever wondered; why do we need these devices in the first place? Join us as we try to answer that very question.

The Importance of Analog to Digital Conversion:

Analog to digital conversion plays a crucial role in the world we live in today. Most signals (e.g. a song or speech) are analog in nature. However, if you want to transmit them all over the world to multiple people at once, or if you want to enhance its quality by removing background noise, you will need to convert them into digital form.

This need to convert analog data into its digital equivalent stems from the fact that our computers and microprocessors can only handle digital data. By converting analog data into its digital equivalent, you open the door to a million different possibilities. Digital data can be read, stored, transmitted and even manipulated (if need be) by computers.

However, just like your voice (an analog signal) needs a medium (in most cases, air) to travel to your audience, digital media also requires a communication channel or medium.

Unlike analog data, digital data cannot be transmitted through the air as its binary data that holds no physical form! Digital data can however be sent to and from devices by using Digital to Analog Convertors (DACs) and Analog to Digital Convertors (ADCs).

The Role of Analog to Digital Convertor (ADC):

The ADC plays an important role in the transmission of data from one device to another. For example, if you’re sending a recording of your voice to a friend, you will need both the ADC and the DAC.

When you press record on your phone, you input analog information to the recorder (in this case, your voice). The phone makes use of an ADC to immediately convert this data to digital form so that it can be processed and edited. The microcomputer then sends this digital data to your target audience using a digital channel of communication like the internet.

However, digital data holds no meaning to your audience. They do not want to hear or see a bunch of 0s and 1s! Therefore, this digital data must be converted back into its original analog form. This is where the DAC comes into play. By transforming this data into its analog form, your audience can play and listen to the recording you sent them with ease! The entire process can be summarized by the following flowchart:

Selecting an ADC:

Unfortunately, the process of selecting an ADC is a complicated task, to say the least! You need to carefully analyze a plethora of different aspects like power consumption, energy rating, resolution, and frequency response, etc. when making your choice.

That being said, the most important factor when choosing an ADC is its sampling rate! Simply put, if the sampling rate of your ADC violates the Nyquist criteria, your system will suffer from aliasing and loss of information!

The Nyquist Theorem states that:

“In order to reproduce a signal without any distortion or loss of data, the sampling frequency must be greater than twice the maximum signal frequency or twice the bandwidth.”

Mathematically,

fs ≥ 2 fm

Where, fm = Maximum frequency in a sample

And, fs = The sampling frequency of the ADC/DAC

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