The LT6013 datasheet states that it is only guaranteed to be stable for gain of 5 or more. Since you are using the .op directive to simulate only the operating point, it may be unable to determine it accurately if the op-amp is unstable. Try a transient sim and see if the op-amp is oscillating. Another point is that this op-amp can only swing down to within 40mV of the negative rail. You aren't very far away from that at 100mV. I suspect that this is not the cause of your problem but I wanted to give a heads up. For LTSpice, I usually keep notes on some general purpose op-amps to use in simulations. Unfortunately I don't have my notes handy but you could consult LT's web site for some gp op amps The ideal op-amp model should work but it can also lead you to think a circuit will work when in reality it won't Sean On Sat, Nov 3, 2018, 4:18 PM RussellMc wrote: > At a glance only, what happens if you reduce the divider resistors values > to say 10k and 1k? > Very much depending on the opamp spec, input bias currents can have an > affect. Input offset is unlikely to be that large. > > > > Russell > > > > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .