[IBIS-Users] problems about extracting IV curves from SPICE model

Hi, everyone.
For my research purpose, I want to extract IV data (pullup, pulldown, etc.)
from the SPICE model of inverter 74lvc04a, and the result is supposed to be
similar to the IBIS IV table. However, for my case, there is a large
difference (around 10 times smaller than the IV table in IBIS file) although
the whole curve trend looks similar. And it exists for all IV curves.
For my circuit connection, let's take pulldown curve as an example, I give
corresponding Vdd voltage source to power suply, ground input and connect
the output to a variable voltage source (V1) and use a current probe to
measure the output current(I1) at the output port. I plot the IV curve I1
vs. V1 and treat it as the pulldown curve. No floating voltage source in the
circuit.
Can anyone tell me what's wrong with my connection?

Thanks and regards,
Yuancheng

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