{"id":15424,"date":"2016-08-26T10:00:19","date_gmt":"2016-08-26T17:00:19","guid":{"rendered":"https:\/\/blog.digilentinc.com\/?p=15424"},"modified":"2016-08-26T15:29:29","modified_gmt":"2016-08-26T22:29:29","slug":"whats-the-point-of-a-dac-and-why-do-i-care","status":"publish","type":"post","link":"https:\/\/digilent.com\/blog\/whats-the-point-of-a-dac-and-why-do-i-care\/","title":{"rendered":"What’s the point of a DAC and why do I care?"},"content":{"rendered":"

If we all live in a “digital” world where seemingly everything is controlled by a computer, why do we still use a digital-to-analog converter (a DAC)?<\/p>\n

Isn’t analog a thing of the past? Why not just use pulse-width modulation (PWM)?<\/p>\n

Despite having used DACs<\/a> on multiple occasions, I found myself questioning their true usefulness when I asked those questions. None of Digilent’s FPGAs <\/a>or microcontrollers <\/a>have a dedicated DAC that is available for general use. On the other hand, pulse width modulation is a technique that takes relatively few lines of code to implement and is very relevant in the working world. PWM also only takes up one digital output pin to emulate an analog signal while a DAC commonly takes up to 3 or 4 output pins.<\/p>\n

\"The
The PmodDA2 (a DAC) all wired up.<\/figcaption><\/figure>\n
\"A
A PWM Circuit all wired up.<\/figcaption><\/figure>\n

To explore this, let’s tackle the first question: isn’t analog a thing of the past? Before we get too far into this (outside of the short answer, which is no), I think we should define what “analog” is. Analog is a way to measure or represent something in an analogous fashion; you get a physically moving object that is a representation of the phenomena you are attempting to measure. Correspondingly, an analog signal is one that represents a physical phenomenon in a smooth and continuous fashion; there is no threshold that needs to be reached in order for the representative value to change.\u00a0<\/em>Digital on the other hand, is either “on” or “off”\u00a0so you need to send out multiple pulses if you want to represent anything besides on or off. Additionally, you have to send out more pulses to emulate more precise analog values.<\/p>\n

But back to the original question.\u00a0While much of the processing of information does solely exist in the digital realm, analog is not a thing of the past. Any sort of motor, whether it’s in a printer, the one that spins the hard drive on your computer, or the motor in\u00a0a\u00a0small robot, uses analog signals to spin at precise speeds. Any\u00a0dimmable display uses an analog signal to get a variable brightness for your screen. If your processing resources are limited, using a DAC such as the PmodDA2<\/a> to set your analog output value (or multiple output values) once and not have to continually send a PWM signal to emulate the analog output, is suddenly a very attractive option.<\/p>\n