High Frequency Active FET Probing DEMONSTRATED

[@CarlVanWormerAE7GD]

The best "cheap-out" scope probe tricks I use with my standard 200Mhz 10x probes are: 1. Touch the scope ground point with your scope probe to see how much “stray” signal your connection method is producing. This can help avoid wasted time chasing the cause of the “bad” signals that are not really there. 2. To see if your scope probe capacitance is screwing with your probed signal, touch the same point with a second probe to see how much it changes your displayed waveform with the doubled probe loading effect. If the displayed waveform changes “too much” then the scope probe capacitance is the most likely cause. You don’t need to monitor the second channel, but it needs to have the ground lead connected to your circuit and be plugged into another scope input (even the external trigger input). 3. To reduce the loading effect of the scope probe capacitance, grab a 1k-Ohm leaded resistor with the scope probe and probe the circuit with the other end of the resistor. This can show a much better representation of the waveform being probed. 4. To reduce “RF” interference on low-level analog signals you are probing, grab a 10k-Ohm resistor with the scope probe and probe the circuit with the other end of the resistor. This will give you a better “BW Limit” function, lower than the scope button for the 20MHz BW limit with only a small additional DC error. 5. For a better understanding of the probing impedance effects in your circuits, use an impedance nomograph to help you estimate impedance ratios for the circuits you are probing (like the ones at www.testecvw.com/carl/CarlMain.htm ) Later, Carl

[@jhonbus]

4:52 "I would not be buying a sold-as-is FET probe off ebay!" Shahriar from the signal path definitely would, and it'd fix itself 2 minutes into the video 😂

[@JustinAlexanderBell]

real

[@myleft9397]

4-5 figures!? It better come in a nice box. Interesting video.

[@pipatron]

You could mention that there are pretty simple active DIY FET probes which are perfectly capable if you don't need perfect calibration. There are hobbyists selling finished boards in the range of $20. I'm very happy with mine.

[@KeritechElectronics]

Gotta love them teeny tiny grabbers! Putting those LEDs on an active probe was a genius move on Agilent's part.

[@grhinson]

"Beyond the bandwith", sounds like the name of a podcast

[@EEVblog2]

Trademark.

[@LawpickingLocksmith]

Beyond Ingham: Chicken dinner?

[@KeritechElectronics]

@@EEVblog2 "The Amp Hour: Beyond the Bandwidth" :)

[@sanches2]

I loved those fish like probes with led eyes at my previous job :)

[@janbrittenson210]

20:26 I think the reduced overshoot with the 1k resistive probe is an artifact; because it discharges the pin driver output there is a smaller switching current, and hence less inductive overshoot. It's not "real" in the sense of the probe somehow being less inductive. You can see there is no difference on the rising edge. I'm sure you're perfectly aware that the inductance is a function of the loop area between the probe and the ground lead + PCB return path.

[@janbrittenson210]

The probe capacitance also matters at lower frequencies. Try probing the pins of a crystal in a 12MHz XO with a 10pF passive probe, for example - it's just going to either stop or skew, or even behave erratically as it repeatedly auto restarts, depending on which pin you stick it on. 10pF also doesn't permit seeing the actual XO waveform, and whether for example it's clipped (overdriven) or under voltage spec. A datasheet will have the correct correct voltage range for integrated XOs that just need an external crystal and load capacitors, and the only way to verify a design is working to spec is with a low-capacitance FET probe. In fact, more generally, they're necessary to probe high-impedance circuits, of which an XO is only one example.

[@markadams2765]

My Rigol Probe not only does it have single, diff ended heads , plus 2 upmarket doggy Dave heads one with a ferrite bead 1 cable. It also contains solder a small ruler and a calibration kit.

[@emmoemminghaus6455]

@Dave OK the DIY Probe behaives differently, but which orobe points to what really happens on the bus?

[@andymouse]

Great question :)

[@MadeInMichigan]

so why not put a 1m ohm resistor (or 10k or 100k or whatever) in your homemade probe? what happens then?

[@sebastian_harnisch]

Main channel content

[@VandalIO]

Yes

[@VandalIO]

Does this work ?

[@padmanabhaprasannasimha5385]

I see probe, I hit like.

[@EEVblog2]

That's what she said.

[@KeritechElectronics]

Eric Cartman likes that!

[@padmanabhaprasannasimha5385]

@@EEVblog2 I walked right into that one 🤣

[@andymouse]

@@padmanabhaprasannasimha5385 :)

[@borayurt66]

Nice... For the price of the cheapest one, you can buy 4 of my current bench oscilloscopes. 🤪🤪

[@tommihommi1]

for measuring the rise time of a random gpio switching off a cheap microcontroller, 1GHz bandwidth might not be enough

[@hermannschaefer4777]

It's quite funny if you order 20x N7002A and don't add "mosfet".. purchase department might have some questions.. ^^

[@paulcohen1555]

They can throw in a nice case for the PRICE OF THE PROBE.😂

[@rb8049]

1pF is often too much.

[@leandrolaporta2196]

4 figures! Are tou kidding me?, That's a ripoff 😮