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A project log for A 1x, 100 MHz, 35 V common mode diff probe

I needed a differential probe for BLDC motor ESC development and adapted Bud's design for my needs

ChristophChristoph 10/13/2020 at 17:150 Comments

No big surprises here: Since many of the parts have very specific values, tight tolerances and low temperature coefficients, I could only use 2 resistor types that i had already. So I ordered the rest from digikey and ended up with a huge pile of almost empty bags:

PCBs and stencil are from Aisler, as well as that piece of 1.6 mm cardboard (I love that!).

The land patterns seem to be made for hand soldering, so I expected the 0402s to tombstone. One did:

That was fixable, and the large tantalum cap in the lower right corner needed a little touch up. Other than that, everything went well. Assembly took about 100 minutes from cutting the opening in the cardboard to reflowed PCB.

Since I wanted to power the probe from a 5V USB port, I added a USB cable. Of course, it had 5V on the black wire and ground on the red one, but M1 is there to keep such a mistake from damaging the probe.

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