Can you make use of an LM3900? I have one here *somewhere*. I think its a quad Norton, not sure how long its been there for.
also have a few canned op-amps etc -Andre ________________________________________ From: volt-nuts <volt-nuts-boun...@febo.com> on behalf of Attila Kinali <att...@kinali.ch> Sent: 27 February 2018 18:25 To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] HP3458 ADC integrator On Sat, 24 Feb 2018 12:59:21 +1300 (NZDT) Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > 1) Reverse the supplies on U4 (in real circuit reversed supplies will fry the > chip.) > 2) Add 10k in series with reset switch > 3) Swap connections to U4 inputs. > 4) Use series shunt switch for reset switch as used in an actual 3458A. > Once done together with swapping in LT1220 for LT1225 rest works as expected > and output slews due to gate current of J1 and input bias current of U1 Ok, I played around a bit more and I think I now mostly understand what's going on. The main problem was really the stability of the opamps chosen. For the integrator to work, the added up gain and phase shift must still fulfill the stability condition (obvious, yes, but.. well I am stupid at times) I am not sure how the intermediate steps in a 3 opamp integrator work, but I guess that should imediatly be obvious once a complete stability analyis is done. Thanks everyone who provided insight and feedback. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ volt-nuts mailing list -- email@example.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- firstname.lastname@example.org To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.