+ Post New Thread
Results 1 to 6 of 6
  1. #1
    Advanced Member level 3
    Points: 5,460, Level: 17
    Achievements:
    7 years registered

    Join Date
    Jan 2012
    Location
    Italy
    Posts
    952
    Helped
    41 / 41
    Points
    5,460
    Level
    17

    PMOS WELL of same bulk potential of different transistor groups

    Dear friends,

    I have different PMOS matched transistors matched in different groups but all they have the same bulk potential (bulk connected to the VDD), if these groups are near to each other is it better to attache both of the well and makes the groups share the same well as much as possible? or may separate wells give better performance ?

    Thank you very much

    •   AltAdvertisement

        
       

  2. #2
    Full Member level 3
    Points: 1,418, Level: 8

    Join Date
    Sep 2015
    Posts
    151
    Helped
    28 / 28
    Points
    1,418
    Level
    8

    Re: PMOS WELL of same bulk potential of different transistor groups

    Only the design engineer can give an adequate answer to your question.



    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 3
    Points: 9,504, Level: 23

    Join Date
    Nov 2001
    Location
    US
    Posts
    809
    Helped
    245 / 245
    Points
    9,504
    Level
    23

    Re: PMOS WELL of same bulk potential of different transistor groups

    It is customary to place matched PMOS transistors in the same well. And I mean physically the same well, not just electrically connected to the same potential.



    •   AltAdvertisement

        
       

  4. #4
    Full Member level 1
    Points: 1,388, Level: 8

    Join Date
    Mar 2015
    Location
    USA
    Posts
    111
    Helped
    20 / 20
    Points
    1,388
    Level
    8

    Re: PMOS WELL of same bulk potential of different transistor groups

    If you put devices in the same well that share a common potential, it’ll reduce layout area. Otherwise you’ll have to ensure you have adequate spacing between the wells to pass DRC. This is especially important when the wells are biased at different potentials. With increasing reverse bias on the wells, their depletion widths expand. If the depletion widths get too close, they can conduct a lot of leakage current or even result in a punchthrough scenario.


    1 members found this post helpful.

  5. #5
    Advanced Member level 3
    Points: 5,460, Level: 17
    Achievements:
    7 years registered

    Join Date
    Jan 2012
    Location
    Italy
    Posts
    952
    Helped
    41 / 41
    Points
    5,460
    Level
    17

    Re: PMOS WELL of same bulk potential of different transistor groups

    Dear friends,

    Thank you for your reply,

    I understand from your kind explanation that there is no difference in electrical proparties if I put them in the same or different well, I am talking about matched transistors with the same bulk potantial, it is only matter for saving the distance between two different well... and also as Suta said, it is becoming like a custom to put them in the sme well



    •   AltAdvertisement

        
       

  6. #6
    Advanced Member level 3
    Points: 9,504, Level: 23

    Join Date
    Nov 2001
    Location
    US
    Posts
    809
    Helped
    245 / 245
    Points
    9,504
    Level
    23

    Re: PMOS WELL of same bulk potential of different transistor groups

    If they really have to match. place them in the same well.



--[[ ]]--