How to do derivative in hspice

[srini.pes]

Hi.,
I have charge expression Q.
I want to calculate the current contributed by this charge Q as I =dQ/dt.

Please provide me the procedure for this.

I came through a option

.measure deriv[]

Will it do the same or different ??
Please clarify..

Thanks

 

[artmalik]

yeah the function is fine. The idea of derivative is to measure the slope of the curve at a certain point of time. So this will work fine for you.

 

[srini.pes]

Thank u
But am doing DC analysis, i don't have any time information to mention as the final time.

 

[artmalik]

The relation between current and charge has to do with Time parameter. I am assuming you are measuring charge, on what parameters you are measuring charge. Because a charge transfer of Q in 5ns will give a different current value compared to charge Q transfered in 10ns. what is the purpose of measuring current. Provide more details as I think you are mixing two things : trying a measure a static parameter which is actually dynamic.

 

[srini.pes]

Actually., am doing one transistor design.
In that they mentioned the current as dQ/dt
I have the expression for Q, as function of Vg,Vs,Vd
Now i want the current dQ/dt.