Capacitor on CMOS IC

Discussion in 'General Electronics Chat' started by sharanbr, Jun 19, 2015.

  1. sharanbr

    Thread Starter Active Member

    Apr 13, 2009
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    Hello,

    How is a capacitor normally implemented in CMOS integrated circuits. Is it through done indirectly using CMOS transistors or there is another way to do this?
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Oxide layer between two layers of metalization if it is a series capacitor, else a single metal layer on oxide to substrate, if it is a shunt capacitor.
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
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    Depending on the aspect ratio of metal lines, you can also use sidewall capacitance from interleaved metal lines on the same layer.

    For supply decoupling, some processes use MIM caps to replace the more traditional device cap (which you referenced) that uses gate capacitance and is more "costly" because it consumes area that could be used for more useful transistors.
     
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  4. DickCappels

    Moderator

    Aug 21, 2008
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  5. sharanbr

    Thread Starter Active Member

    Apr 13, 2009
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    Thanks a lot ...
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    There are many ways to implement capacitors on CMOS ICs. If you want high capacitance and can tolerate high nonlinearities then you make FET caps using the gate capacitance of a FET where the gate is one plate and the drain/source (which are usually tied together) form the other. You can also use interconnect layers to get linear capacitors and there are a number of ways to do that depending on your needs and the area constraints you are working under.
     
  7. sharanbr

    Thread Starter Active Member

    Apr 13, 2009
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    Thanks. Probably this is in the domain of Analog engineers. I am just taking baby steps in Analog design ...
     
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