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My favorite design idea of all time…

The editors of EDN will tell you that the Design Ideas section is the most popular section of the website, this goes back to the print editions, where that was the first section that most if not all readers turned to first upon getting a new issue. This was so popular in the 1990s that Linear Technology put paid advertisements into this section with their tear-out Design Ideas. I still have some of those in my archives.

Design Ideas was, and are, a community where average ordinary readers could contribute to the magazine some concept, clever circuit, or solution to a problem with only a few hours of work on their part to draw it up and write 500 or so words on it.

Of course, the concept of design ideas predates EDN or any other electronics magazine. My first encounter with the design idea concept was the ARRL publication QST [1] where they had a “Hints and Kinks” [2] section in every issue. Even then, it was the most interesting section of the magazine to look at. ARRL also published the “Hints and Kinks” collection in book form, and I remember checking them out from the library on many occasions, others liked it too as it was a well-dog-eared book.

But the design idea concept predates even QST. The publication Mechanics Illustrated also had many pages devoted to reader submissions. Figure 1 shows a design idea from the “Popular Mechanics” of January 1914 [3].

Figure 1 The concept of reader-submitted solutions to problems goes way back. This one was published in the January 1914 edition of “Popular Mechanics” magazine. Source: Popular Mechanics

So, I am sure that the concept of the design idea goes back to probably the first magazine ever printed, where some editor turned a “letter to the editor” into a reoccurring section of the publication.

Whatever the original origins, the concept was and remains very popular.

My most memorable design idea of all time

I’m not sure of the exact date and I can’t find the original publication or author (perhaps some reader will be able to locate that), but the most memorable design idea that I ever saw had to do with bypassing the input stage of an IC op-amp with a couple of JFET’s making a kind of Frankenstein hybrid—discrete, IC amplifier (Figure 2). As I recall, the idea dated to the mid-1980s, give or take a decade.

Figure 2 My favorite design idea drawn from memory. The cleverness of using the LM318 for all the backend circuitry along with a user selectable input stage just had universal appeal for me and others as it was used many more times in the coming years.

This was a perfect combination in my mind, the ability to use whatever front end you wanted with the simplification of all the output stages by using the rest of the LM318s internals.

I used this concept once or twice and in some test fixtures because it was fun and the National Semiconductor LM318 was a very capable op-amp for its time with settling times to the 10-bit region in less than a microsecond. I was also familiar with the 2N5912, which was a low-noise, low-capacitance dual JFET in a TO-100 package, so I used that in my implementations [4]. We bought that transistor from National Semiconductor also, so instead of making one sale, National Semiconductor made two sales from that design idea. They should have given the original author a commission.

Other people liked it too.

While I have no idea about who invented this first, the basic idea spread all over the place. In 1992 National Semiconductor published application note 299: “Audio Applications of Linear Integrated Circuits” [5]. This application note contained an audio preamplifier that used the LM394 NPN super matched pair and an LM318 to make a low-noise phonograph preamp (Figure 3).

Figure 3 National Semiconductor used their LM394 Super matched pair as the input stage for their take on the design idea Source: National Semiconductor Corporation

Then, in 1986, Linear Technology published Jim Williams’ take on the idea in application note 21 [6]. There, Jim used the dual FET idea and, where I used to match the JFETs for drift, Jim used a low drift amplifier in a Goldberg topology [7,8] to zero the drift of the added JFETs (Figure 4).

Figure 4 Jim Williams’ take on the design idea circa 1986. Here Jim extended the idea to include low drift as well using the Goldberg topology Source: Linear Technology Corporation

The bypass the op-amp front end design idea concept shows up in conjunction with other op-amps as well, like the NE5534 classic audio op-amp. This was a universally popular concept for its time and caught many an eye besides my own.


I once worked for a fellow who told me to write our instruction manuals interactively, that is to engage the user in a way that they felt part of the process. I think that is what this design idea did; it engaged the designer to be part of the process and not simply use the op-amp, but to extend it and customize it to one’s own liking.

At any rate, the design idea concept is as “old as the hills”, as they say, and is not going away anytime soon.

I am also sure that many of the ideas that I have seen since my childhood have directly influenced my designs and workshop practices over the years, even if I can’t directly pinpoint the source of those ideas (Figure 5).

Figure 5 Many of our design and shop practices stem from design ideas that we have seen in the past. The cover of the ARRL’s 1974 “Hints and Kinks” had a great idea of how to accurately drill a chassis. I still drill my chassis like this today. Source: eBay image

“If I have seen further, it is by standing on the shoulders of giants.”
– Sir Isaac Newton, 1675


  1. QST Magazine, American Radio Relay League.
  2. The word “kinks” as a simple “Idea” also has origins to machining, hunting, and fishing, going back to before the early 1900’s and many publications can be found using this term.
  3. Popular Mechanics, Page 129, January 1914.
  4. 2N5912 Data Sheet, National Semiconductor Corporation.
  5. “Audio Applications of Linear Integrated Circuits”, AN-299, National Semiconductor Corporation, 1982.
  6. Jim Williams, “Composite Amplifiers”, Application Note 21, Linear Technology Corporation, 1986.
  7. Goldberg, Patent.
  8. The first design idea that I ever published also used the Goldberg Amplifier Principle. “BIFET op-amp and bipolar op-amp join forces for low drift and fast slewing”, 400 Ideas For Design, Vol 4, 1980, Hayden Book Co.

Steve Hageman has been a confirmed “Analog-Crazy” since about the fifth grade. He has had the pleasure of designing op-amps, switched-mode power supplies, gigahertz-sampling oscilloscopes, Lock In Amplifiers, Radio Receivers, RF Circuits to 50 GHz and test equipment for digital wireless products. Steve knows that all modern designs can’t be done with Rs, Ls, and Cs, so he dabbles with programming PCs and embedded systems just enough to get the job done.

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