Get the White paper from the Cadence web site..
Functional Verification of a Differential Operational Amplifier..
that was ONE of the many Opamp specs I addressed in that paper for the 2001 International Cadence User Group.. since ICU owns the copyright, it can't be added to this website, as far as I know..  But that predate's some nifty new features like,
stability analysis, mismatch analysis, and the VSDE environment to manage simulation results and give PASS/FAIL judgements on your design..
I was, at one time, hoping to do a re-write.. but haven't managed to get around to it, and its no-longer in my MBO's..
jonathan