Stats

  • Locked Locked
  • Replies 2
  • Subscribers 143
  • Views 14230
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

VNPP Description

Conorp

I find the description of the VNPP function a bit unclear. It doesn't seem obvious to me what it's going to return.

I found this function through the calculator by choosing "vn" and choosing a device in my schematic and then a drop-down menu appeared to let me choose the noise parameter. 

e.g: I want to plot the total noise voltage generated by my transistor. I select "vn" in the calculator and choose my transistor and then choose total. I then plot this and see that the units for the noise voltage are [V^2/Hz].

It doesn't seem obvious to me that the units of my noise voltage should be in that form based off the documentation. It should really say that it's returning the Power Spectral Density in which case this makes sense. However the calculator chose this function for me when I chose "vn" as opposed to "vn2" which is where my confusion stems from. So I was originally expecting the units to be [V/sqrt(Hz)] having chosen "vn".

I was wondering also could someone clarify what "double level" refers to in the context of a noise parameter? I couldn't find anything from searching in support.

See VNPP documentation, IC Design Environment Version, and Calculator screenshot below.

Virtuoso Custom IC Design Environment: IC6.1.7-64b.500.21

VNPP

VNPP(t_namet_param[ t_dataDir ])

=> g_value / nil

Description

VNPP accesses any double level noise parameter available in the PSF database.

Arguments

t_name

Name of the component.

t_param

Name of the noise parameter.

t_dataDir

Directory containing the PSF files(results). When specified, this argument will only be used internally and will not alter the currently selected results.The default is the currently selected results directory.

Value Returned

g_value

Value of the specified noise parameter.

nil

Specified noise parameter not found.

  • The documentation is pretty poor on this. It looks like it's just been taken from the code which doesn't explain it very well. The units are in V^2/Hz (not V/sqrt(Hz)) and the "double level" is trying to say (badly) that you're specifying both the component and the noise source name (e.g. "total" or "id" or "rd" or similar). The VNP function only takes the instance name and gives a family of curves with each contribution (again in units of V^2/Hz).

    From what I can see, the "vn2" button in the calculator doesn't seem to work - but I agree, I'd expect vn2 to trigger the VNPP function (maybe) to trigger sqrt(VNPP). There are also (confusingly) access functions called VN() and VN2() (in uppercase) but these give the total output noise in V/sqrt(Hz) and V^2/Hz respectively, so don't make sense to have in the schematic selection panel since they don't need any selection from the schematic.

    I'll talk to R&D about this.

    Andrew.

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.