The Ideas for Design series is part of our Library: Article Series.
After Electronic Design asked me to contribute something to this special issue, all kinds of possibilities ran through my mind. After all, it had been 40 years since my first ED article, which was itself an Idea for Design (IFD), “Gated Amplifier Uses FET in Feedback Loop,” in the Jan. 4, 1968 issue.
So, what’s an IFD? The snappy answer is that it’s one of Electronic Design’s most popular editorial features. But more germane is the fact that the IFD distills the “what, why, and how” of an EE design challenge, summarizing an example solution into a one- or two-page writeup, often ready to be applied just as described. Typically, they aren’t heavily theoretical, though they are often long on practicality. So, what to do and what to say became big questions.
Hitting the Books
I began with a “stimulation by observation,” a review of my huge collection of various IFD tear sheets accumulated over the years (not all of which have been adequately catalogued, I hate to admit). In addition to this IFD rat’s nest, the review also included more formal sources.
I had three of the four published 400 Ideas for Design books (References 1-4). Then, I also found the very first of this series online, via AbeBooks (www.abebooks.com), and snapped up a copy. The series began in 1961, and these four hardbound books span four- to five-year periods from 1961 to 1979. Later on, there were smaller “Best of Issue” IFD magazine supplements (References 5-7). All of these are recommended reading, should you be able to find them.
Should it matter how a design was done in the 1970s or 1980s, versus an approach today? Yes! First, there is the adage of being ignorant of history’s mistakes, thus condemning one to repeat them. But what is so useful about a historical review of designs lies in extracting the optimization and evolution towards maturity.
Keep in mind that many of these published IFDs are also what I call the “timeless” variety. The timelessness comes from the inclusion of a basic principle that will generally continue to be useful, even if the specific parts shown in its execution might become obsolete.
For example, take families of op-amp precision rectifiers, of which there are many IFD examples over the years. Each time a newer, faster op amp appears, another variant shows up. Computer programs can also fall into the timeless category of IFD. The mathematical routines will remain valid even if executed within another host program. So, these IFD principles can continue to be valuable, even though exact design details may change.
The IFD Evolution
A strong impression that I came way with after reviewing a couple of decades worth of IFDs is how much (and how many) things have changed, in terms of how designs are physically executed. This wouldn’t always show up within an IFD, but it does offer perspective on where we are and perhaps about where we’re going. Today, we have evolved into different ways of doing many engineering tasks and using different parts to build our electronic assemblies. A lot of this is good, but some of it is not.
For example, there’s greater use of computers and advanced prototypes. We have much more powerful computers to aid us in executing our designs faster and with greater efficiency. But some engineers seem to feel that a successful Spice run alone validates a circuit design. In the long run, a well-executed breadboard/prototype is the only real proof of circuit design validity. The higher the frequency of operation, the truer this becomes.
Fortunately, many IC vendors now routinely offer evaluation boards that use high-frequency techniques like ground planes, controlled transmission lines, and low inductance bypassing, as well as surface-mount (SMD) components and other factors. This really does help control the undesired parasitics and speeds the design cycle. Of course, another part of the design process aided immensely by the more powerful computer is the printed-circuit-board (PCB) design.
Additionally, there are more IC components, with much broader capability. To take op amps as one familiar point of reference, we’ve come from Bob Widlar’s 1965 709 to a vast array of parts with hundreds of megahertz of bandwidth and outputs of a hundred milliamps today. Switched-mode video amps make a gated amplifier no more complicated than wiring up a logic control pin—or, from a general functionality point, a wide array of parts that run rail-rail (input and/or output) and feature low (or very low) current consumption.
Yet considering all IC types, a radical revolution in packaging has happened since the old TO-99 can originals. For the most part, this broader availability of packages is also good. In some cases, though, it does impact performance.
For instance, low-power op amps are noisier and have less bandwidth—a design fact of life. Another con during the design cycle is that it complicates breadboarding, since tiny SMD parts are extremely difficult to handle manually. Yet this in itself is a two-edged sword, as it tends to force the prototype into a PCB layout, which is that much closer to the end item—and thus more real-to-life.
Design cycles are faster now, too. Today’s designs, created by definition within the Internet era, can take advantage of tools simply not available in the past. A Google search can bring up dozens of relevant patent documents or design papers in a few moments, all for free. Everything published in a given IEEE discipline is just about as easily accessible, at a reasonable cost. Magazines such as Electronic Design are increasingly providing editorial content online, although sometimes the breadth of coverage is less than desirable.
Of course, circuit junkies such as myself would like to have all IFDs as well as feature articles online in their complete original form (as a PDF) and supported by useful indexing. The first two examples just cited could be used as models for this type of researching. If you doubt this, just check it out. But alas, another two-edged sword arises when one tries to find useful design examples via a more general Google search, using other than such higher-level archives.
A very high percentage of what comes up online is limited in quality, and some of it is outright garbage. A caveat emptor is definitely due here, given the dubious relevancy of too many Web postings. In this regard, it should be obvious that the original article on the topic is to be sought, not a watered-down adaptation posted on a circuits smorgasbord Web site. This research often takes real work, but there isn’t really any substitute for it. A couple of mouse clicks just won’t be enough.
The Internet also touches the design cycle in other positive ways. Who orders parts or even reads datasheets from a paper catalog anymore? Fast, efficient Web sites such as those set up by Digi-Key and Mouser make the prototyper’s job much easier, and PDFs of datasheets have reduced the number of trees necessary to get through a design task. All of this is to the good.
And, if it ain’t broke, don’t fix it. Another point noted in my review of older IFDs was that many popular parts still remain so, even after 40 years! Those older IFD books feature familiar transistor parts like the 2N2222, 2N2907, 2N3904, and 2N3906. I still use these today, as do many of you out there.
Likewise, early op amps like the LM301A, 741, and CA3130 can still be found. Then there’s the number-one linear IC in lieu of all those op amps, the 555, still around and as popular as ever. And similarly, 4000 series CMOS parts are still being used. Whether or not any of these would be the best choice in a new design today is another matter, though.
However, the popularity of such ancient parts even today might boil down to meeting the minimum required specs at the lowest cost. When that’s the case, 40-year-old parts like 2222s and 3904s still get used. They hit a performance sweetspot on bang-for-the-buck (or pennies, actually). Another plus is that, unlike the originals, today’s variants come in multiple-unit packages, tiny small-outline ICs (SOICs), and so on, making them a greater bonus on utility.
This “if it ain’t broke, don’t fix it” theme reminds me of an apt story. The late Tom Sweiger, an engineer friend wiser than me back in those 1960s design days, told me that he didn’t need to use the (then new) IC transistors, like the CA3046. He said his own favorite 2N3904 “works fine and does the job!” That was true back in the late 1960s, as it still is today.
A Dream Archive
While I do have a lot of IFDs accumulated in paper and PDF form, I wish I had more. I also wish I had them well-catalogued as to author, function, date, and other criteria. On the one hand, that sounds like a pipe dream. On the other hand, take a look at what Google has done with books and patents, and think again. Certainly, it is possible.
The Ideas for Design series is part of our Library: Article Series.
References
1. Edward E. Grazda, Editor, 400 Ideas for Design, 1961-1964, Hayden Book Company, 1964.
2. Frank Egan, Editor, 400 Ideas for Design, Vol. 2, 1965-1970, Hayden Book Company, 1971.
3. Morris Grossman, Editor, 400 Ideas for Design, Vol. 3, 1971-1974, Hayden Book Company, 1976.
4. Morris Grossman, Editor, 400 Ideas for Design, Vol. 4, 1975-1979, Hayden Book Company, 1980.
5. Steve Scrupski, Editor, Best Ideas for Design, Electronic Design special issue, Oct. 24, 1996.
6. Steve Scrupski, Editor, Best Ideas for Design, Electronic Design special issue, Oct. 23, 1997.
7. John Novellino, Editor, Best Ideas for Design, Electronic Design special issue, Oct. 22, 1998.
An Electronic Design author since 1968, Walt Jung most recently penned “Walt’s tools and tips,” a practical, analog-oriented column that ran in 1997 and 1998. He also was named to ED’s Engineering Hall of Fame in 2002. In addition to numerous applications articles for various publications, he has published many books. the most popular of these is The IC Op Amp Cookbook, in print since 1974. He retired from Analog Devices Inc. in 2002 after editing the ADI book, Op Amp Applications (Handbook). He is a Fellow of the Audio Engineering Society and an IEEE member as well.