OPA211 noise analysis questions

Dan Andersen

Other Parts Discussed in Thread: OPA211, OPA2301

My customer is doing some simulation of the OPA211 vs OPA230. Schematic is shown below:

They are trying to simulate output noise at higher ( up to 10Mhz) frequencies and observe some weird bump in output noise at these frequencies:

The expectation is that the OPA2301 noise would be higher due to the higher voltage and current noise, but according to the sim, that doesn't happen around 10MHz.

Can we shed some light as to what is happening? Is this real behavior or some sort of glitch in the spice model?

We also get the following error in the sim model - and we are not sure if this is related or not:

Thanks,

Dan

over 8 years ago

0 Dan Andersen over 8 years ago

TI__Genius 11450 points

Correction to first sentance - OPA2301, not OPA230. Schematic is correct. I have sim files I can share as needed.
Thanks,
Dan

0 Britt Brooks - Online Design Tools over 8 years ago in reply to Dan Andersen

TI__Mastermind 41310 points

Dan,

The issue has been confirmed. I'll pass this on to the Signal Chain team for evaluation.

I did not see the warning shown, however.

0 John Miller - Sensing over 8 years ago in reply to Britt Brooks - Online Design Tools

TI__Mastermind 38875 points

Dan,

The OPA211 model does indeed show the noise bump.
We will look into it further and will post a reply to this thread when we have a solution.

Regards,
John

0 Victor Salomon over 8 years ago

TI__Expert 3900 points

Hello Dan/All,

Just wanted to point out for future search reference that if needed you can make your Noise Model using SPICE Noise Sources, as suggested by Op Amp Noise guru Art Kay, in his reply to this E2E Thread "modeling individual op amp noise."

Art mentions in his reply: "You can use spice “noise sources” to set voltage and current noise to whatever level you like. These sources allow you to set 1/f and broadband noise independently. See attached file. Also, resistors automatically include thermal noise. The details behind how to use the noise sources is given in TI Precision Labs (see link to noise 6 below)." He also provides:

TI Precision Labs - Op Amps: Noise 6

TINA Noise Sources revC.TSC (which is also found in TINA-TI's EXAMPLES folder in the installation folder, "DesignSoft/Tina 9 - TI/EXAMPLES/").

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OPA211 noise analysis questions