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I am using AD625 as differential amplifier since the input offset voltage is very low. I completed the designing part but I didn't find any simulator where I can simulate AD625. How to simulate AD625 using LTSpice? Or is there is any simulator available where I can simulate AD625?

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3 Answers 3

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There is a SPICE model for AD624, but not for AD625. The two amplifiers are very similar, importantly the same GBW and Vos, but not identical, as the 624 incorporates a few extra resistors on the input to simplify gain control.

Open the two datasheets side by side. You may be able to modify your 625 circuit to incorporate the 624 resistors. If you can identify those input resistors in the SPICE file, you should be able to delete them from the model, and bring out the internal nodes.

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  • \$\begingroup\$ so your saying download spice model for AD624 and change it in a such away that its functionality becomes similar to AD625? \$\endgroup\$ Jun 27, 2017 at 11:37
  • \$\begingroup\$ @AkshayKumar Yes. As far as I can tell from the data sheets, the silicon inside is identical, the only difference is the few extra resistors around the input. If your 625 circuit is consistent with the placement/use of those resistors, then you can use it as is. If not, those resistors ought to be easy enough to find and remove from the file. \$\endgroup\$
    – Neil_UK
    Jun 27, 2017 at 12:30
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I am using AD625 as differential amplifier since the input offset voltage is very low.

Let's start here - I disagree if you look at the bigger picture for many circuit scenarios and also consider output offset voltage and drift: -

enter image description here

And compare it with something like the AD8221 (that does have a spice model: -

enter image description here

It beats the AD625 hands down in most applications and temperature related drift is particularly good. The AD8221 is a little bit noisier but maybe this is not a problem for your application - only you can say. Gain versus frequency are about the same for both devices.

The AD625 doesn't appear to have a spice data sheet because it is a little bit oddball in the way it uses the gain sense pins.

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Did you google it? Here it is http://www.analog.com/en/design-center/interactive-design-tools/error.html

I doubt there is a model for LTSpice. You should probably port existing SPICE file to LTSpice. There is plenty on how to do that online.

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  • \$\begingroup\$ yes sir.I saw that design calculator but i was looking for simulation models.. \$\endgroup\$ Jun 27, 2017 at 11:42

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