Well mostly the front end of amp*
I'm at home so I can't post a pic of the lab amp in AoE3, (pg 274?8?)
Win, I hope it's OK to post a dropbox link to a figure from your book?
In this case, I (think, I) need both ends floating, and low current**
I've been trolling Digikey for FET instrument amps. (I should make a map of Vos vs Ibias***) My ascii art is (a bit) better than me trying to explain it. one side of IA, in total four(or two?) R's and four diodes.
V(+)supply-+ | _ D ^ |\ Vsig-+-Rs--+--|+\ | | | \ Rin _ | \ | D ^ | >--- Gnd | | / V(-)-------+ (etc. traditional input protection.) So Rin = 10Meg (or infinity?) and Rs is 1k (at the moment, 10k is ok, but adds noise... most IA's stink noise-wise, I've hardly looked at the (IA) noise.)
So if Vsig is 100V then Rs has to dissipate Vsig^2/ Rs... 1W @Rs=10k!
OK Win, I was going to complain that your 50k resistors were too big.... never mind about that.
Hmm, what about resistors as fuses?
George H.*Though I'm happy to talk about how to organize the back end of the signal chain.
**And low V offset, though in some sense the offset is OK if you can measure it.*** there's also an Ioffset number, (not sure what it means)