Check out how to build a high speed oscilloscope probe that measures 125MHz signals better than commercial probes. Paulo Oliveira writes: [via]
Some years ago, I learned some valuable lessons about probing high-speed signals. Somehow, mistakes have a way to sticking in your mind and we call them “experience”. Most modern oscilloscopes come with a “high-bandwidth” 10X passive probe. Figure 1 shows the venerable Tektronix P6139, 500 MHz, 8pF probe. At first glance, a “500 MHz probe” might seem adequate to probe say, a 125 MHz clock signal right? Wrong… We will see why with a practical example showing the issues you run into when trying to probe such a signal. Later in the article, I’ll also show how a surprisingly simple and affordable DIY passive probe can outperform even the best 10X passive probes for this particular application.
Homebrew highspeed lo-Z scope probe – [Link]