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Fingers and multiplier of MOSFET

jun1119

Hi 

What is the meaning of finger and multiplier in a MOSFET as we can see in the properties of a MOSFET?

[URL=http://img12.imageshack.us/i/mosj.png/][IMG]img12.imageshack.us/.../URL]

 

I would highly appreciated if there are some diagrams and layout to be shown.

Thank  you

  •  Hi there

     I have no idea what the multiplier does, in fact if have never used this at all in 16 years.

    The finger parameter on the other hand is very helpful if you want to draw big transistors.

    Changing the finger parameter simply creates parallel transistor gates to exactly the amount  you

    have entered.  Image you have a device in the schematic 400u wide but you don't have 400u

    of space in either direction but you have a nice little rectangular spot left. You create a single

    transistor 20u wide and change the finger parameter to 20. This yields in a 400u transistor

    with 20 "fingers" a 20u, drain/source areas already merged. You just have to do the wiring.

    Simply try it !

     

    Best Regards

     

    Andi

     

  • This depends in the implementation of these parameters

    In most cases I have seen
    - number of fingers is a pysical paramter which lets you fold
      your mos width a long with to several mos with width/finger
      and shared S/D areas.
    - the m is a multiplication factor for the simulator which
      multiplies the current though the devices.

    Bernd

  • Hi,

    The m is the multiplication factor.

    In Layout XL, for transistors, the m from the schematic is used to create multiple layout instances with common parameters.

     i.e. for eg., a schematic instance M0 with total_width=6u, length=1u, fingers=3 finger_width=2u m=5

    will result in 5 layout instances:

    M0.0: total_width=6u, length=1u, fingers=3 finger_width=2u

    M0.1: total_width=6u, length=1u, fingers=3 finger_width=2u

    M0.2: total_width=6u, length=1u, fingers=3 finger_width=2u

    M0.3: total_width=6u, length=1u, fingers=3 finger_width=2u

    M0.4: total_width=6u, length=1u, fingers=3 finger_width=2u

    Rgds,

    Vikram

     

  • Multiplier - number of Parallel MOS devices


    Finger Width - width of each gate finger/stripe


    Fingers - number of poly gate fingers/stripes used in layout

  • Hello, I generate a schematic with a single MOSFET and set the multiplier (m) to 8. However, when I generate the layout from the source, Layout GXL brings me a single device, not 8 devices with the same size. When I run LVS it fails and tells me that the properties of the devices do not match (the device in the schematic view has 8 times larger width than the device in the layout). What can be the problem with this m factor and generating the layout from the schematic source? Thank you very much in advance for your answer.
  • First of all, the forum guidelines ask you not to post new questions on the end of old (2 years old in this case) threads. Secondly, it's pretty hard without seeing your set up - it could be numerous things. Suggest you contact customer support at http://support.cadence.com

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