The Filter Wizard: 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.
Are you 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 their problems; leave them something to do so he or she feels — and can display to the 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.
Kendall Castor-Perry, systems architect and member of the technical staff at Cypress Semiconductor, is an experienced analog circuit designer and much-published communicator of theory and method in many electronics disciplines.
This article first appeared on EE Times’ Planet Analog website.
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