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OPA145: OPA145 Spice model

Ken Armitage

Prodigy 70 points

Part Number: OPA145
Other Parts Discussed in Thread: OPA2145

I'm looking to use the OPA145 (or OPA2145) in a new design which uses very low Voltages. The supply rails would be +/-3.3V. According to the data sheet the part looks like it should be good down to +/-2.25V. However when I tried using the spice model, I can't get the part to work properly below about +/-5V. Is this a known bug in the model or does the part really have a problem working down at low supply Voltages..? I've tried both the Tina spice tool and the LTSpice tool but they both give identical results.

over 4 years ago

0 Raymond Zhang1 over 4 years ago

TI__Guru 56121 points

Hi Ken,

Vcm has specific requirements, see the attached image below.

/cfs-file/__key/communityserver-discussions-components-files/14/OPA145-E2E-07282020.TSC

Best,

Raymond

0 Ken Armitage over 4 years ago in reply to Raymond Zhang1

Prodigy 70 points

Hi Raymond

Thank you so much for your very prompt reply.

I also found the amplifier worked correctly at +/- 3.5V.

If you try 3.3V it no longer works which is confusing.

Do you see the same?

Regards

Ken

0 Raymond Zhang1 over 4 years ago in reply to Ken Armitage

TI__Guru 56121 points

Hi Ken,

At +/-3.3V, it still works, but the output has a large offset somehow, the it is still operating correctly or linearly above and below the offset.

I need to check with model engineer and see if there is an error in the model.

Best,

Raymond

0 Michael Steffes over 4 years ago in reply to Raymond Zhang1

Guru 48395 points

In the meantime Ken,

I happened to have a file with the initial Rev A 2017 model,you might give that a try. OPA145 2017 model.TSC

0 Raymond Zhang1 over 4 years ago in reply to Michael Steffes

TI__Guru 56121 points

Hi Ken,

My bad! I did not pay attention to the common mode voltage at V+ pin, which is sitting at GND. The model is correct.

If you have any questions, please let me know.

/cfs-file/__key/communityserver-discussions-components-files/14/OPA145-E2E-07292020.TSC

Best,

Raymond