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Analog Angle Article

The positive/negative feedback conundrum

I heard yet again a presentation by human-resources, “dealing with people” specialist that the key to a good working relationship is generous application of positive feedback and very limited use of negative feedback. All the while, I was thinking: hey, I know that negative feedback is the key to system performance, and positive feedback leads to instability, oscillation, and worse.

I really don't know to what extent you should balance the two kinds of feedback in dealing with people, since I suspect that it's very dependent on who you are working with and the specifics of the situation. But I do know that engineers have devoted uncountable hours to working out feedback issues, aided by Bode plots, the Nyquist criteria, and more. Keeping the response in the proper part of the plane is essential, and you want negative feedback, in the right amount, and with the right dynamics. Negative feedback stabilizes, it linearizes, it keeps our components, circuits, and systems happy and well-behaved.

Of course, you can trade off some of the negative feedback for faster response time, but you have to be careful. And you can get fancy with non-linear feedback schemes, as long as you really know what you are doing. But go into positive feedback territory, and you've got major headaches.

So I'll maybe consider the advice when dealing with people, but ignore the lure of applying it to system designs. And maybe this difference in perspectives on positive feedback is part of the reason that engineers and HR people often don't agree on the best way to handle people, or the right thing to do?♦

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