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How to make stack for transistor

RM202605273230

Dear Sir/Ma’am,

I am currently trying to implement transistor stacking in Cadence Virtuoso in such a way that when I increase a parameter (for example, ns), the transistor internally creates stacked devices while still displaying a single transistor symbol in the schematic.

Initially, I attempted to achieve this by:

Adding an ns parameter in the CDF,

Writing a callback function using SKILL code.

However, I observed that increasing the parameter was not actually generating additional stacked transistors internally. Later, I came to understand that this functionality may require the use of a PCell implementation rather than only CDF callbacks.

I also explored modgen, but I learned that it mainly assists in generating proper stacked structures in layout and does not automatically create stacked devices in the schematic through parameter changes.

Could you please guide me on the correct procedure for implementing transistor stacking in the schematic using PCells? 

Any guidance or resources would be greatly appreciated.

Thank you for your time and support.

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  • RM202605273230

       Thank you for thread support and   

    Could you please give the solution for my query if you know the solution 

    Thank you 

  • Andrew Beckett
    in reply to RM202605273230
    RM202605273230 said:
    Could you please give the solution for my query if you know the solution

    The answer is to create a PCell - I have an example of doing this both with PCell Designer (which would be the simplest approach) and also using SKILL. I'm still on vacation so will send something when I'm back in the office on Monday.

    Andrew

  • RM202605273230
    in reply to Andrew Beckett

    I hope you're referring to the stack of the transistor in schematic by increasing the ns factor i dont know to how to make it so I was just guessing this could be done with pcell 

    So solution you are gonna give me on Monday that would be helpful to me 

    Thank you 

  • RM202605273230
    in reply to RM202605273230

     Hi,

    Just a remainder message when you are available to send the example

    thank you

  • Andrew Beckett
    in reply to RM202605273230
    RM202605273230 said:
    Just a remainder message when you are available to send the example

    I did have a week of actual work actions to deal with on my return from vacation; the community forum I do in my spare time...

    I had the two example to upload, but something is wrong at the moment and I cannot upload any images or files. I will work with our IT to fix this.

  • RM202605273230
    in reply to Andrew Beckett

    okay thank you 

    i appreciate your that you reply in community forum in your spare time

    Thank you

Reply
  • RM202605273230
    in reply to Andrew Beckett

    okay thank you 

    i appreciate your that you reply in community forum in your spare time

    Thank you

Children
  • Andrew Beckett
    in reply to RM202605273230

    Two approaches (both using transistors from gpdk045 as an example):

    PCell Designer

    In PCell Designer, the structure of the PCell would be as follows:

    Here's what an instance looks like with sfactor set to 5:

    This example can be imported into PCell Designer (note, you need the PCD100 license for this) using this file (it's a gzipped tar file containing the pcd.txt to import):

    seriesMOS.tar.gz

    SKILL PCell

    For this, you will also need either abInvokeCdfCallbacks.il or CCSinvokeCdfCallbacks.il (from article How to call CDF callbacks procedurally from SKILL to update CDF parameters?). If you have the one from the article, change the call to abInvokeInstCdfCallbacks within the code below to CCSinvokeInstCdfCallbacks. The comments at the bottom of the code show how to invoke the code to create the PCell.

    https://community.cadence.com/cfs-file/__key/communityserver-discussions-components-files/38/abCreateStackedTranSchPCell.ils

    Regards,

    Andrew

  • RM202605273230
    in reply to Andrew Beckett

    while placing the pcell with sfactor 5 it will show 5 transistors or only 1 ?

    i am looking to use 1 transisotor symbol but have stacked inside it with sfactor 5

  • Andrew Beckett
    in reply to RM202605273230
    RM202605273230 said:
    while placing the pcell with sfactor 5 it will show 5 transistors or only 1 ?

    In both cases you'd have a symbol as normal - that would show the single transistor. The approaches described above create a schematic PCell alongside the symbol - so if you descended (readonly) into the instance, the resulting schematic would show as many series-connected transistors as sfactor/ns whatever the parameter is called.

    Regards,

    Andrew

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