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I am working on a simple phase-lag circuit schematic using LT Spice, and, due to some project specifications, would like to simulate the behavior of the circuit specifically with FET-Input Operational Amplifiers from the TL08x family.

My problem is that I have been trying to add said op amps as new components by downloading the .301 file available online (in places such as the Texas Instruments website) and creating symbols associated to each subcircuit. Everything seems to work just fine for the TL081, but I've noticed that the TL082 and TL084 files seem incorrect: they're literally just identical copies of the TL081. The 082 is supposed to have 8 ports, since it's essentially an IC with two TL081s inside, but the .301 file only has five ports! Same thing for the TL084.

I've attached screen-captures of the pin distribution I was expecting, based on the datasheet for the TL082, as well as the LTspice files, showing how the subcircuit description claims to be for a TL082, but only results in a single, 5 pin op amp. What's going on here? Am I missing something incredibly obvious about how these files are supposed to be used? Did someone just copy-paste the subcircuit description of the TL081 onto the 082 and the 084, upload it to the TI website a decade ago, and leave it there?

Datasheet pin distribution for TL082 Macromodel subcircuit and port loadout

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  • \$\begingroup\$ This is actually quite common, and you'll rarely see it the way you originally expected it. One of the main reasons is this pinout order you see is [almost always] standardized, so you can use a generic SPICE opamp symbol. In this case, using opamp2 found near the end of the [Opamps] folder in LTspice will work for this library file. If you want to create a custom subcircuit which includes all the individual amps, you can follow this guide: ngspice.sourceforge.io/ngspice-eeschema.html#multi \$\endgroup\$
    – Ste Kulov
    Commented Apr 20, 2023 at 6:03

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Typically SPICE models are per-part. Repeat the model for each part in the package. Using them on a block component (not divided into parts) is not recommended.

LTSpice isn't a full EDA tool anyway, so you miss nothing by using individual TL081s in a model, where you would use -2 or -4s in the actual PCB design.

A downside of this method is you certainly can't get weird interaction effects, like saturation of one amp affecting bias of the other; but that doesn't apply to this type I believe (it's largely a relic of now-long-obsolete types I think), and anyway I doubt a manufacturer would craft a SPICE model so detailed as to include such obscure/deleterious effects anyway. (Which is also to say: beware that what you get in the model file, need not, and in general does not -- or even, cannot -- reflect the full reality of a given part.)

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If you look at the datasheet, you will know that they are identical opamps with different numbers in one package. Therefore, they share the same Spice model.

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