Hello everybody,

When I tried to use "slewRate" function in waveform calculator of Cadence Analog Design Environment , I found I could get two different SR values for the same ramp of the same curve by using two options seperately, which are either

"initial value Y at X" and " Final value Y at X"
or
"Initial value Y (value)" and "Final value Y (value)"

All others are under same configurations (opamp structure, curves, and the same ramp). For example, below show what I got for two cases:

slewRate(VT("/Vod") 1.96e-5 t 2.5e-5 t 10 90) = 6.018M
slewRate(VT("/Vod") -2.52 nil 2.04e-7 nil 10 90)=-2.02M

In above two equations, the Y values are the exact values for those at the time being.

If we look at the abosulte value of the above two results, they are 3 times different.

Can someone point out what 's reason for this?

In addition, I have looked up the "Overshoot Function", "Settling Time Function", and "Slew Rate Function" in Cadence "Waveform Calculator User Guide", I found that the definitions for "Initial Value" and "Final Value" are all same in the above three cases. Am I right? Because, in user guide, it didn't show the figure for Slew Rate function, and it only shows other two figures. I would like to be confirmed that I have done correctly.

Thanks a lot.

ethan