Mind / Iron
by Bryan Bergeron, Editor ;
There’s a Chip for That
Need a generic desk and chair by tomorrow morning? Head to IKEA.
Want to learn cabinet making so that you can make a custom desk and
chairs? Then get to work planning and stocking your workshop.
It's the same with circuits. If you need a compact, affordable circuit
tomorrow that performs a common function, say, voltage doubling, then
you'll likely find a dozen or more affordable ASICs (application specific
integrated circuits) that will satisfy your requirements — with no or few
However, if your goal is to learn how a particular circuit works and how
it can be modified to suit your particular needs, then you should consider a
circuit made of discrete components, transistors, and generic ICs. The end
product will likely cost more in terms of component prices, printed circuit
board real estate, and your time. However, you'll have an opportunity to
Of course, you have to make the most of this. If you simply insert the
parts into a breadboard, solder everything into place, and then apply
power, you'll waste the moment. For example, let's say you have a voltage
doubler circuit based on the LM555 timer chip. You can change the
frequency and duty cycle and external component values to assess how the
changes affect output voltage and current.
The process vs. product tension isn't the only reason to consider single
chip solutions over discrete component circuit design and construction.
Some of the newest chips have exceptional specifications: higher efficiency,
lower voltage requirements, less potential for interference, better thermal
regulation, lower noise floor, etc. Sometimes it comes down to weight. For
example, I've been working with quadcopter controllers, and every extra
ounce of circuitry means about five minutes of less flying time, less
maneuverability, and less space for something else.
Often, it's a matter of focus. Let's say you've built a LIDAR that requires
a voltage doubler. If your focus is to learn how to apply LIDAR to robot
navigation, then don't waste your time designing or building a low level
supply circuit. Pick up a voltage doubler chip and get to work on the LIDAR
I've found the major hurdle in using an ASIC over a handful of discrete
components is determining if my wish-chip exists. My first go-to resource is
Digi-Key. They maintain a good (albeit incomplete) catalog of special
purpose chips at reasonable prices. My second stop is Mouser — another
online supply company. Prices are usually a tad higher than Digi-Key, but
they also handle a slightly different IC product line. Failing to find
something in my top two list, I turn to the chip suppliers directly, such as
TI and National Instruments. Most of these companies provide powerful
search engines indexed to their products.
In closing, there's nothing inherently wrong with using discrete
component circuits in your projects. It simply depends on what's best for
your budget, the components you have on hand, your experience with new
and old ICs, and whether the circuit is for your personal use or destined for
the masses. However, make an informed choice. Check out which ICs or
components best fit your needs. If, after a first exploration, you can't find
the chip you're looking for, keep looking. New ASICs are announced daily.
6 SERVO 03.2013
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