<azonenberg>
61ps 20-80%, 88ps 10-90% rise time. pretty happy with that
<azonenberg>
https://www.antikernel.net/temp/ad4-v0p2-s21.png S21 response. 4 GHz -3 dB bandwidth, but if you compensate for fixture losses (not currently de-embedded) i think 5 GHz is going to be very achievable
<azonenberg>
i only need another half a dB and i think the fixture probably loses that much at 5 GHz
<azonenberg>
5 and 10.3125 Gbps with probe/cable/fixture measured response de-embedded (I cannot currently separate them, time domain gating or similar will help when i get to that point)
<electronic_eel>
the AKL-AD4 looks really nice, congrats!
<azonenberg>
yeah i need to add a trimmer for the DC offset then figure out how to de-embed fixture losses (I think it's already 5 GHz, i just can't prove it yet)
<azonenberg>
then maybe some EM shielding
<electronic_eel>
which resistors are you using on the tips? iirc you were waiting for custom made ones for some of your probes
<azonenberg>
but yeah i don't think it needs much. for something where the first board spin let out the magic smoke, it's doing well :p
<azonenberg>
Vishay HML01. right now i am using 100 ohm
<azonenberg>
i got 15 of them i've been gradually trickling out into designs for R&D, recycling as i respin boards
<azonenberg>
i ordered a hundred more that just shipped (order placed in feb)
<azonenberg>
i also ordered 450 ohm at the same time
<azonenberg>
the idea being to combine my current 350 + 100 series strnig into a single part
<azonenberg>
those have not yet shipped and i have not been able to get engineering samples
<azonenberg>
so i don't know if it will improve performance or not
<azonenberg>
i have to wait until they ship, whenever that is
<electronic_eel>
ah, ok, so the new resistors could still improve the design
<azonenberg>
yes. and the pt5
<azonenberg>
the ad4 is basically two pt5s feeding into an adl5569
<azonenberg>
nearly identical tip layout
<electronic_eel>
so, what is the downside of the AKL-AD4 against the AKL-AV1? why use the AV1 and not a AD4 with one side tied to ground?
<azonenberg>
The AD4 has 500 ohm DC loading like a PT5
<azonenberg>
the AV1 is 5M ohm
<electronic_eel>
ah, ok, sure, then the AV1 has it's place
<azonenberg>
exactly. that's why i made it
<azonenberg>
all of the good GHz amplifiers had on die termination
<azonenberg>
which made high input impedance hard
<azonenberg>
so i figured i dont care, i'll do like 1K diff / 250 ohm common mode for the diff probe
<azonenberg>
thats good enough for most applications
<azonenberg>
then make the AV1 for when you really need ultra low dc loading at the cost of bandwidth
<electronic_eel>
next step: use skywater to make your own high impedance ghz diff amp ;)
<azonenberg>
sky130 is not exactly an analog process
<azonenberg>
nor do i have any skillz at making discrete analog transistor layout