Just Add a Transistor

There’s a classical marketing story that most business students get to hear. Yes, I was such a student once upon a time; don’t think any less of me for allowing a few dollars to get mixed up with those dBs. The food company General Mills created the fictitious persona of Betty Crocker as the face of its customer support, and her image became so popular (second only to the First Lady of the time) that they decided to use her name as a brand for a range of cake mixes. Despite high approval ratings in focus groups, the cake mixes sold badly. To cut to the end — yes, this is a blog, not a marketing lecture — industrial psychologists believed, after some scratchy-beard time, that housewives suffered feelings of guilt at using a product that produced a cake with so little effort.

So, General Mills reformulated the cake mix. They removed the powdered egg and instructed the consumer to whisk in their own egg instead. Sales rocketed — apparently because housewives were now that bit more invested in their interaction with the product and felt they were contributing some value in the process.

Shifting in your seat and wishing I’d get to the point about why this is relevant to modern electronic design practices? Well, it’s all about integration, the integration of a rich toolbox of lovely ingredients inside a system-on-chip device that you can program to do pretty much anything you want. That’s exactly the type of product that my employer produces, and I spend most of my time either architecting systems that use these devices or helping to define cool blocks to put into future devices. (Hint: search for “PSoC”).

I’ve sometimes described our products as being so easy to use, in the creation of almost anything electronic, that it hardly feels like work anymore. A few years back I spun this out into a potential advertising campaign in which the hard-pressed engineer gets home, after a tough day trying to solve his design problems with the conventional approach (a thousand parts from a hundred suppliers, if you’re lucky), and retires downstairs to his den. “Poor guy,” thinks his understanding wife, “all he wants to do is have a beer and go watch the game after another tough day at work.” But in fact, he’s down in his home lab, building some cool stuff with an evaluation board for one of our products, because it makes the engineering process fun again — the reason why he chose that career in the first place, rather than follow his classmates into law, finance, or medicine (and hence solvency).

But (they say you shouldn’t start a sentence, let alone a paragraph, with but, but…) recently I’ve begun to wonder. I’ve been reminded of a lesson I learned early in my career, from my first boss: let your customer do something. Don’t try to solve all his problems; leave him something to do so he feels — and can display to his boss — some ownership in the end product. Let engineers do a bit of engineering once in a while, in other words.

Now, I don’t feel too guilty. My company’s devices really simplify and streamline routine electronic system engineering, and that’s a good thing. But sometimes you’re presented with a task that’s can’t quite be fitted onto such a programmable device entirely through the use of internal structures, and some additional external active components are needed (on top of the auxiliary passives that are always going to pop up here and there).

So, ladies and gentlemen, I give you (with all trademarks acknowledged) the “Betty PSoCker” Circuit Design Challenge: Just Add a Transistor. You’d be surprised how many interesting additional circuit functions can be wrested from my employer’s already-versatile programmable SoC product if you just add a cheap vanilla transistor to your design. It happens that most of the cases I’ve looked at recently have used a regular npn bipolar transistor; these are easily available in very small smd packages — duals too, if you want to push the boat out and add two transistors! Check out both ON Semi and Diodes, Inc. (who are clearly underselling themselves, because they make far more than just diodes!) for examples of teeny-weeny devices. You can use a pnp, or a MOSFET. Even a JFET, if you’re feeling retro! Just make the circuit do something that it clearly could not have done without the addition of a three-legged friend.

In the next few blogs I’ll talk about some of the circuit functions I’ve worked on where adding a transistor or two to an existing highly integrated mixed-signal device can unlock a new level of functionality or performance. Get ready to share your own thoughts!

8 comments on “Just Add a Transistor

  1. antedeluvian
    April 10, 2014


    As a long time user of PSoC (I started with it back in~2001) I have used many transistors to surround the device. I have always said that the best part is the fun you have with the device. It takes me back to the early days when there was a new periipheral every week. Now you get to create your own peripheral (or at least wire) the peripheral within.

     I recently used the PSoC5 on my BluDAQ “oscilloscope” as described in my blog Trace Signals from Behind Closed Doors and was the ideal chip.

    I look forward to you sharing your stories with us. I have just downloaded the Cypress app-notes on creating your own components as a precursor to a home idea I have. I hope you go on to describe some of that as well.

    Incidentally the upcoming part 3 of my blog on temperature measurement touches on the PSoC3/5 as well.

  2. Davidled
    April 10, 2014

    Transistor is getting small and small. It could be a bit in the CMOS level in the future.  I image that transistor function would be a part of component material. Then, I am wondering what type advanced TR could be used in the semiconductor chip. However, recently, I did not see many research paper related to TR for a while.

  3. RedDerek
    April 11, 2014

    I recently finished a design where I had several LM3914 LED drivers. One challenge was to synchronize all the dimming with one control. This was accomplished with a few external components and a current mirror. Separate current mirrors went to each of the LM3914 RefOUT pins to have the same current draw and thus dim each of the drivers in unison. A simple extension of a single product application.

  4. kendallcp
    April 11, 2014

    LM3914?  Now there's a name I haven't heard in a very long time…

  5. samicksha
    April 15, 2014

    I agree you, The IC was introduced back in 80s and still available, a single LM3914 can drive up to 10 LED displays on its outputs.

  6. etnapowers
    April 15, 2014

    It's a good example of robust design. Time after time the LED requirements, in terms of input/output voltage ranges, supply current, changed and the product is still suitable to supply LED displays.

  7. Sachin
    April 16, 2014

    I have noted with interest the comment on the LM3914. For a while I almost thought it was going to become obsolete since very few of us use it anymore, but my interest was spurned by another piece I read on wearable technology and it seems that they are going to be in use even more in future. I guess they will definitely have to be much smaller if they are to make any significant impact in this relatively new world of wearable tech.

  8. Sachin
    April 16, 2014

    A regular EE like myself will almost always have one or two deadlines hanging around his neck (in fact I hardly ever find time to read posts here let alone write a comment) so maybe, in a way, it is a nice thing that company's like yours Kendall give us ready to swallow components and save us time. But in view of the points you raised, I believe the best approach would be to segment the market and give the busy EEs the ready stuff. The guys working on personal and side projects have more time on their hands so they will probably welcome the chance to experiment more with PSoC.

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