why the cascode configuration can solve the problem gate-drain breakdown?

Discussion in 'General Electronics Chat' started by anhnha, Sep 8, 2013.

  1. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    This is a conventional cascode configuration amplifier:
    [​IMG]
    Here is an excerpt in "Self-biased cascode RF power amplifier in sub-micron technical field" .
    http://www.google.com.vn/patents/US6515547
    I don't understand why the cascode configuration can solve the problem gate-drain breakdown. Please explain.
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Simply don't believe in every word you read in the internet. For sure we can split Vdd into two Vds junction. Or we can use low power MOS as a M1 and high power MOS (M2). We use cascode configuration because this configuration eliminates the Miller effect.
     
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  3. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    Last edited: Sep 8, 2013
  4. Jony130

    AAC Fanatic!

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  5. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    I am confused because their symbols.
    I knew Miller effect but I want to know whether you agree with answers in the page above about how cascode configuration reduces Miller effect.
     
  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    I think that those symbol represent real components not parasitic parameters.

    cascode configuration reduces Miller effect by a reduction M1 voltage voltage.
    M1 gain = (1/gm2)/(1/gm1) = gm1/gm2
    Also M2 work as a common gate configurations the Miller Cgd multiplicative effect does not exist. Because gate is short to GND for AC signal.
     
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