Moin attila I'd start with simulating and understanding the integrator in the 34401A, its a little simpler but still has a coupe of opamps in the integrator. Then analysing the GBW requirements of the various opamps used in the HP3458A shoul become somewhat clearer.
Bruce > > On 24 February 2018 at 04:51 Attila Kinali <att...@kinali.ch> wrote: > > Moin, > > I am trying to understand how the HP 3458 integrator of its > dual-slope ADC works, as it's a bit more complicated than > a simple, single opamp integrator. As you can see from the > attached picture, it consists of 3 opamps (U1-U3) for the > integrator itself, and another for the slope amplification (U4). > Unfortunately, I do not get what U2 and U3 are doing, much less > why they are needed. > > So I tried to simulate it in LTspice. But, the circuit oscillates. > In both, the reset state (when the integration-C shorting switch is > closed) > and the integration state (though, less wildly so). I guess, this > is because I replaced the LM6361 and AD848 by the LT1225 but do not > understand why, or respectively, which of the differing parameters of > the LT1225 causes this oscillations. > > Would someone be so kind and give me some hints? > > Thanks in advance > > 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 -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
