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Do OpAmp spice models that also have the Null Offset pins broken out exist?

I'm looking for a model of TL071 and all i'm finding is the basic 5-pin model.

I'm trying to wrestle with an existing design. The original designer was using the null offset pins to zero the the output with a non zero input. I want to see if i can slightly improve the span of the zero capability. I'm struggling to find any information on how much range the null offset pins have and how to calculate the actual null offset voltage. My hope was to use a spice model that has the pins to help me out.

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  • \$\begingroup\$ Offset null feature was used in the old days to compensate for unwanted offsets due to manufacturing variance. How does that feature relate to simulation? Are you trying to determine how much offset adjustment range is available? \$\endgroup\$ – MarkU Sep 6 '16 at 20:10
  • \$\begingroup\$ It's rare when you'll find a model that comes with a close-to-reality implementation under the hood, most of the time they are, for the large part, behavioural. If you do find one that models the transitors, you'll find that your simulation will go quite slow, if not slower, which is not unexpected. These said, I don't think you'll find such a model for TL07x/08x, but I could be wrong. \$\endgroup\$ – a concerned citizen Sep 6 '16 at 20:11
  • \$\begingroup\$ If you're planning to do something tricky like inject signals into the offset null pins (or use the power supply currents of an op-amp for that matter) you're probably on your own. \$\endgroup\$ – Spehro Pefhany Sep 6 '16 at 20:20
  • \$\begingroup\$ @MarkU that's exactly what i'm trying to do. I updated my post to more accurately reflect my needs. \$\endgroup\$ – vini_i Sep 6 '16 at 23:17
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So, if you look at the datasheet of the TL072, on page 13 it shows where the offset pins attach. What you are essentially doing when you do the recommended offset circuit (on page 12), is putting new resistors in parallel with the 1080Ω resistors.

The absolute most you could change this is going to be if you were to remove the 1080Ω resistor on one leg or the other by connecting that pin directly to V-, and then to attach the other to V+. This would obviously be a little silly, but it would rail the output of the op amp.

I wouldn't recommend using any V+ voltage on the offset pins, but you can get a larger range in the zeroing by using a smaller pot, and a smaller tail resistor than the recommended circuit offers.

Hope this helps. If you want more help, we are going to need more information about what you are doing.

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