Products > Test Equipment
> 1 GHz DIY differential probes
snoopy:
The probe heads on the commercial probes such as Keysight and Tektronix are usually built using strip-line techniques on special pcb materials with consistent dielectrics used for rf design so there is quite a bit of R&D in them to get them right. I just picked up a differential probe off ebay for a good price but they are getting hard to find at good prices. Considering the new ones cost megabucks your best bet is to look for used ones that are in working order.
Marco:
Those aren't high impedance though, not unless you count a couple hundred Ohms as high impedance.
GHz is in that sweet-spot where you can still have something relatively high impedance and general purpose.
dietert1:
The offers of Keysight may be well competitive, but they forgot who are their customers: engineers and scientists. Sorry, they cannot address me with a TV spot talking about a spiral inductor and ESD protection. They don't offer a solution compatible with various makes of scopes.
The calling price of a generic 1.5 GHz differential probe seems to be $ 1500, see http://www.significantdevices.com.au. Any hands on experience?
Marco:
--- Quote from: tggzzz on October 15, 2018, 01:39:31 pm ---Or from a few bits of coax and a combiner, e.g. http://emcesd.com/pdf/cd94scr.pdf
--- End quote ---
More expensive than a bunch of BFU660F's though. How about something simple like this? Is the simulator really giving me that bad an impression of how it would work with a tight layout and some =<0204 components? R1=R2=0 is only useful for say 10s of mV of input, probably want to bias the bases to ~4V with opamps instead of resistor dividers, might want to clamp R5-R8 with Schottkys.
PS. that Deltasense probe has nice specs, large voltage range and input impedance.
Cerebus:
--- Quote from: Marco on October 16, 2018, 06:22:41 am ---Those aren't high impedance though, not unless you count a couple hundred Ohms as high impedance.
GHz is in that sweet-spot where you can still have something relatively high impedance and general purpose.
--- End quote ---
What are you calling "high impedance" in this context, bearing in mind that 1pF across an input @ 1GHz would equate to 159 ohms, and that the stray capacitance across an 0603 part is around 0.04pF and an 0201 part 0.02pF (the latter being ~8k @ 1 GHz)?
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