[SI-LIST] Re: using spice to calculate driver output impedance

Ah ok the vector math makes a lot of sense, I don't know where the
30Ohms comes from though.  Taking this same route does this then mean
that the on die capacitance (C_comp of the driver) presents a certain
amount of impedance to the signal that can also be represented as a
vector that I can add to my total Zout?  

Thanks
Eric

BTW I did this equation which I think is right to add the inductance of
the bond wire.  Zbond+Zdriver = (14.5+j0) + (0+j8.8) = 16.9Ohms.  You
made me pull out my text books to relearn that one :)  Thanks again for
your help.



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Steve Weir
Sent: Wednesday, February 23, 2005 8:14 PM
To: ericsilist@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: using spice to calculate driver output impedance

Eric, the inductive reactance will not add linearly.  Do the vector 
addition and you will find that the resistor value will be a lot closer
to 
the 35.5 ohms that the resistive slope would lead to by itself.  Off the

top of my head, I think you will find 30-33 ohms about right.

Steve
At 04:11 PM 2/22/2005 -0800, eric steimle wrote:
>Hi all, I'm having some trouble thinking of the right
>way to calculate driver impedance using spice.  I have
>finally a functioning model of the driver in question
>and I've been able to run some simulations with it.  I
>was hoping that there might be an accepted way of
>calculating driver impedance out there that I don't
>know about, or perhaps some literature you could point
>me to.  Any help would be greatly appreciated.
>
>Best Regards,
>Eric
>
>
>
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