Building an ‘almost-GHz’ Differential Oscilloscope Probe #oscope
Thanks to Christer Weinigel for sharing this on his blog – be sure to read parts 2 and 3 for some further results.
What I really wanted was an active differential probe which should be able to look at a 500MHz signal at a couple of volts or so with decent fidelity. To do that I wanted a probe with about one GHz of usable bandwidth. I have an old Tektronix 11801B scope with two 20 GHz sampling heads with 50Ω single ended inputs that can handle signals which are 1.0V peak-to-peak so that’s what I wanted the probe output to be compatible with. The probe must attenuate the signal so to not overdrive the inputs and to make things easy to calculate I decided on letting the probe have a 1:10 attenuation.