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Extracting Noise Plots of Isolated Devices using Single Simulation

KGh94

Hello,

I created a small test bench with two transistors. The two transistors are completely isolated from each other. In the noise simulation setup, I am forced to define an output node. If I define the output of one transistor, I am not be able to see the noise plot of the second transistor. This doesn't make sense because I expect the noise parameters (especially flicker) to be dependent on technology or DC parameters.

I am extracting the noise plots using vn in calculator. Is there a way I can get the noise plots for both transistors with a single noise simulation?

Best regards,
Karam

  • Andrew Beckett

    Hi Karam,

    This does make sense, because the noise analysis (in fact all the noise analyses) are intended to compute the noise at a given output node (or an output current) and the noise parameters are actually the output-referred noise contributors from each device. This is because the analyses insert a bunch of noise sources, and compute the transfer function from these noise sources to the given output, multiply that transfer function by the magnitude of the noise source, and then sum up all the noise powers at the output to give the total output noise. So if one of the transistors is not connected to the other path, there will be no contribution to the output noise.

    There is a newer feature which allows you to compute "noise separation" - it's at the bottom of the noise form (pnoise has had this for many years, but standard "AC" noise did not). This will then allow you to get at the the noise at the source each component, the transfer function, and the output-referred noise. Note that this is in the results browser, or via the Direct Plot form, but when in this mode the Results->Print->Noise Summary doesn't work as it gets confused by the additional data in the simulation results. Not sure if this is really what you want, but might be worth a look. It's not really intended as a means of running multiple noise simulations though - the right way to do that is to define more than one noise sim - which ADE doesn't support, unless you use multiple tests in ADE XL or Assembler, or use an include file to define the second noise analysis statements (and then you'll need to figure out how to get to the results - easy enough with the results browser).

    Regards,

    Andrew.

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