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  1. #1
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    on-resistance of a mosfet

    Hello everyone

    I am trying to plot the on-resistance of a mosfet (switch) operating at 100GHz using cadence .

    can you please help ?


    Best regards.

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  2. #2
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    Re: on-resistance of a mosfet

    On-resistance is a DC parameter. At 100GHz you are looking
    for an on -impedance- which is a complex number, and it is also
    shunted at both ends (and the middle, if you care to get really
    fine grained) by complex capacitances (losses).

    Now the DC on resistance doesn't care about small signal high
    frequency riding on it, it "is what it is". But "it is" shunted by
    Cds across, Cdb and Cds aside and all it's worth is a rough idea
    of how low Zds might be (but Ld, Ls, Cds all meddle).

    The phase relation between V and I is unlikely to be 0 degrees
    at 100GHz. That makes mag(V)/mag(I) not the same thing as
    DC OP calculation of VDC/IDC. Different cast of characters.

    I think you're probably after something related to Ron, but
    different, and how it ought to be expressed / presented might
    depend on who's asking, about what specifically.



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  3. #3
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    Re: on-resistance of a mosfet

    Quote Originally Posted by dick_freebird View Post
    On-resistance is a DC parameter. At 100GHz you are looking
    for an on -impedance- which is a complex number, and it is also
    shunted at both ends (and the middle, if you care to get really
    fine grained) by complex capacitances (losses).

    Now the DC on resistance doesn't care about small signal high
    frequency riding on it, it "is what it is". But "it is" shunted by
    Cds across, Cdb and Cds aside and all it's worth is a rough idea
    of how low Zds might be (but Ld, Ls, Cds all meddle).

    The phase relation between V and I is unlikely to be 0 degrees
    at 100GHz. That makes mag(V)/mag(I) not the same thing as
    DC OP calculation of VDC/IDC. Different cast of characters.

    I think you're probably after something related to Ron, but
    different, and how it ought to be expressed / presented might
    depend on who's asking, about what specifically.

    Actually I could estimate it using simple ac analysis (with transistor biased in triode region)
    I measured the small signal ac current at the drain(ac voltage source applied at the drain) then take the Y admittance expression which is Y=I/V ≈(1/Ron)+jwCout

    Then Ron=1/Re(Y) ,

    the result is confirmed by the Input impedance simulation of a passive mixer first receiver.



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