ADA4700 missing nodes error

We needed to evaluate an Analog Devices ADA4700 high voltage operational amplifier and proceeded to download the SPICE model from the Analog Devices website. When it was loaded into an existing design created with Linear Technologies LTSpiceIV the software presented with the following error: –

Ada4700: Missing nodes(s).

A quick Google search revealed that others had experienced the same problem but none of the posts found provided a clear answer that did not involve experimenting with other software tools or changing the analysis settings; neither of which appeared to be necessary.

Solution

The SPICE model was examined and it was found that the first line was either not commented out correctly (as far as generic SPICE modelling is concerned) or was a header appropriate to a specific modelling tool.

After commenting out the first line by adding a * to the first character the model worked correctly without an error in the circuit being simulated.

Conclusion

It’s not clear why Analog Devices published the model with this generic SPICE error but one can only assume that their own simulator tools allow such a first line or ignore it. Either way the solution turned out to be remarkably simple in the end once the problem was understood but it would be nice if all models could be made generic and tested on a number of common simulators.

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