IBIS Series MOSFET Models - questions

From: Stephen Nolan <s-nolan1@ti.com>
Date: Thu May 18 2000 - 09:25:02 PDT

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 Thu May 18 09:25:53 2000

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