Today it seems that everything electronic is digital—a reasonable assumption considering it’s hard to find a turnable knob anywhere and values are displayed in digits everywhere. The underlying assumptions, at least for those without a technical bent, are that digital is modern, analog is archaic (the way things were done before we had something better), and there’s probably no analog “stuff” in electronic products anymore. Fortunately for the designers who work with analog components and the manufacturers that make them, this is far from the case, and it’s likely to remain that way.
After all, the earth and its inhabitants are analog. So, the goal of converting something from analog to digital form is an attempt to re-create the original as faithfully as possible. Of course, from an electronics perspective, once this is achieved, it opens new horizons for designers because much more can be done with a digital representation of an analog source.
But just because something can be converted to the digital domain doesn’t mean it should be. Just ask the audiophile who still uses vacuum tube amplifiers and whose media is the vinyl disc (which, it should be noted, is making a comeback).
Indispensable Devices
Analog components are, consequently, essential—digital devices simply cannot do certain things, at least not yet. For example, state-of-the-art analog-to-digital converters (ADCs) are incredibly capable devices and able to convert analog signals at very high frequencies to digital form. Frequencies above say, 12 GHz, are nevertheless too high right now for even the best ADCs to convert in order to capture signals off the air without downconversion. ADCs also require analog circuits to help in the conversion.
Then there are switch-mode power supplies, which are still analog as high current cannot be handled by digital electronics. And although digital filters hold many advantages over their analog counterparts, they still often need to convert the input signal from its analog form. Analog anti-aliasing filters are required before the ADC in oversampled sampled-data systems, as is a reconstruction (anti-imaging) filter after the digital-to-analog converter (DAC). Analog filters also have a fraction of the latency of digital filters, so they’re faster.