Re: IBIS Series MOSFET Models - questions

Stephen,

The figure in the IBIS specification is electrically equivalent to yours,
although your version is easier to understand, in my opinion. The spec
shows two swept sources with a DC offset between them. I prefer your notion
of one fixed source and one swept source, closer to the hardware that would
actually be used.

I would like to see the diagrams also showing the attachment of the gate to Vcc,
since it currently appears that the entire circuit just floats up and down with the
sweep voltage. Then again, maybe the swept source should be attached between
the source and gate, since we are attempting to sweep Vgs.

By the way, has anyone found one of these series switch models available for
public use?

Mike

Stephen Nolan wrote:
>
> Question 1,
>
> In IBIS Version 3.2, Section 6, "Keyword: [Series MOSFET]" it states that
> "C_comp values are ignored for [Series MOSFET] models." How do you account for
> the Cio(off) and Cio(on) characteristics of the FET in the IBIS model?
>
> Question 2,
> In IBIS Version 3.2, Section 6, "Keyword: [Series MOSFET]", and Section 9.5,
> "Series MOSFET Table Extractions", it says that the voltage applied to the drain
> of the MOSFET is Vds, a fixed voltage difference between the drain and the
> source. Quoting from section 9.5:
>
> Vds is held constant by having a fixed voltage Vds
> between the drain and source nodes.
>
> However, the drawing shows a fixed voltage source between the drain and GROUND!
>
> | +----------------------------------------+
> | | |
> | | Ids = Table Current |
> | | ---> |
> | +---<---| |--->----------+ |
> | d |_____| - s | + |
> | --+-- Vgs +---+---+ +----+----+
> | | g + | Sweep | | Vs + |
> | | Vs | |Fixed Vds|
> | +---+---+ +----+----+
> | | - |
> | GND GND
> |
> | Example of Series MOSFET Table Extraction
>
> I could see how this would result in a Vds voltage if Vs + was swept, so that it
> was always equal to the swept Vs+Vds, but it says "Fixed", not "Sweep".
>
> Shouldn't this drawing be as follows for a true Vds supply?
> | +---------+
> | + | Vs + | -
> | +-----------+Fixed Vds|------+
> | | +---------+ |
> | | |
> | | Ids = Table Current |
> | | ---> |
> | +---<---| |--->----------+
> | d |_____| - s | +
> | --+-- Vgs +---+---+
> | | g + | Sweep |
> | | Vs |
> | +---+---+
> | | -
> | GND
>
> --
> Regards,
> Stephen M. Nolan
Received on Fri May 19 06:16:42 2000