> What is the simplest way to measure the output impedance of a buffer
> given just a spice netlist?
Since CMOS buffers are generally very nonlinear, the first
problem is to decide what you mean by "output impedance."
Example: Zout is the value of pull-up resistance to Vddq
that the driver can pull down to Vddq/2
Example: Zout is the slope of the V/I curve at the supply
intercept.
Example: Zout is Zline minus the series resistance that
gives a first-incidence amplitude of Vddq/2.
For all of these the answer is pretty clear as soon as you
choose the definition; just simulate the output under the
given conditions and constraints.
-- D. C. Sessions dc.sessions@tempe.vlsi.com