RE: Differential voltage probes 2

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Wall Richard Wayne by way of Terry Fritz <teslalist-at-qwest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>


Terry,

 > Note my other post were a single 150MHz amp does that differential stuff
on
 > chip ;-))  With single small 5000V SMD resistors now available, we might
be
 > able to really push this thing up into the MHz.
 >
 > http://hot-streamer-dot-com/temp/DiffProbe11.gif

Notice the almost exact same design of my instrument Op amp and figure #41
in your above gif.  This architecture provides matching symmetry straight
through on both sides.  I feel we should try and maintain this scheme
through out using the figure # 41 scheme.


 > Two things we probably won't have in that case are pots and range
 > switches.  They would just be "complex impedances" at RF frequencies.  We
 > would have to keep the signal paths very small and very short.
Everything
 > would be surface mount...

A voltage shifter can also go to either the non-inverting input of IC-3 or
IC-4. It's just a variable voltage divider across Vdd (Vss) and ground.
The wiper goes straight to the non-inverting input.  Shouldn't create too
much "complex impedances".
We need to assure that when a common DC or AC signal is applied to both
inputs simultaneously we can adjust for the output to be zero.


 > Finn is also hinting that he could do boards if needed ;-)

Excellent.

RWW