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How to find the higher order derivative terms (gm2,gm3,go2,..) and cross-modulation terms (go11,go12..) in IC616

RFStuff

Dear All,

I want to find the non-linear harmonic terms of a MOS tarnsistor.

To this end I wan to find the derivative term gm2=d^2i_ds/dv_gs^2, gm3=d^3i_ds/dv_gs^3...

Also I need to find the cross-derivative terms g012 = d^3 i_ds/ (dv_gs . d^2v_ds), g021 = d^3 i_ds/ (d^2v_gs. dv_ds)...

Is there any simpler way I can find out in IC616 ?

  • The models don't output these higher derivatives. The second derivative you could use the approach discussed in 

    Why transconductance gm exported from DC operating point is not same as dids/dvgs?
    Could anyone one explain why transconductance gm exported from DC operating point is not same as dids/dvgs? I tried to simulate the circuit below and plot gm in two ways. The first one is use gm operating…
    By in Cadence Technology Forums > Custom IC Design
    2 replies
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    (of course you'd need to use the deriv function of the deriv). However, that only works by ensuring that Vd doesn't vary at the same time as Vg so you can isolate them. 

    I think it would be quite hard to measure the "g012" term you mention because you need to isolate the variables. I've never come across anyone asking for this (or even having a need for it).

    That said, I see you've asked exactly the same question to customer support via case 46012000 which appears to have been logged at pretty much the same time as posting here (unless I'm seeing time different time zones in how things are reported). I found this when I was searching to see whether it had been asked before. The Forum Guidelines tell you NOT to do this. If people do this, I will tend not to expend time answering their questions here, as we all have limited time and having two separate AEs looking at the same issue is not efficient.

    Regards,

    Andrew.

  • Dear Andrew,

    I apologize for the posting though I posted here thinking that some other member of the forum who might have done this could guide me.

    I assure you now  onward I will not post the query both in SR and in the Forum.

    Kind Regards,

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