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OPA820 noise at 10+ MHz

Other Parts Discussed in Thread: OPA820

Hi,

The datasheet for OPA820 gives noise curves only to 10 MHz although the part has gain out to several hundred MHz. Does the noise remain flat above 10 MHz? Using the PSpice model I seem to see the noise rising starting at about 10 MHz but I don't know if that is for real. I will check on the lab bench soon but it would be helpful to have a general answer in advance.

The application is simply an inverting gain ~ -1 using Rf=499 Ohm.

  • I suppose it would be useful to show the simulation result which is puzzling me. I am using the OPA820 PSpice model in LTSpice. I made the simplest possible test circuit and ran a noise simulation and see the noise rising very significantly above 10 MHz, reaching 35 nV/sqrt(Hz) at 100 MHz. Will the real part show this behavior? Or is there an issue in the PSPice model? Or somehow in LTSpice's running of it?

    By the way, the high frequency noise seems to originate from device _r53 in the OPA820 PSpice model subcircuit.

    Any insights here will be greatly appreciated, thank you.

  • Hello Gerard,

    Thanks for bringing this to our attention. I checked the OPA820 in the lab and the noise stays flat. Looks to be a problem with the model. I have notified the modeling/tools team to look into this.

    -Samir