Probing High-Speed Digital Designs

(Originally published in Electronic Design Magazine, March, 1997)
Have you ever tried to debug a broken signal that only worked when your probe was touching it? Join the crowd. It's like a badge of honor. It means you work on really fast systems. Then again, it may just mean you need a better probe. The one that you are using just isn't up to par, or the way it is being used is inappropriate for the task at hand. To help solve such problems, this article will explore some ways to characterize their behavior, and the trade-offs inherent in various probe styles. It will even describe how to make a resistive-input probe that performs well into the gigahertz range.