Differentiation in hspice

[srini.pes]

Hi to all

In my circuit i have a current contributed by a charge, described as dQ/dt.

In verilogA there was a direct command for differentiation as ddt() .,
Is there any command to compute d/dt in hspice.

i have seen one command like

.measure deriv ....

but, it will calculate the d/dt of a signal at a particular time.



Hope this was clear.

Thanks & Regards
SRINI

 

[amitjagtap]

I dont think so that there is such command.....How it is if you use the derivative using op-amp circuit in simulation....It will do the same thing...

 

[FvM]

I dont think so that there is such command.....How it is if you use the derivative using op-amp circuit in simulation....It will do the same thing...

Yes, you'll find the same thing suggested in the HSPICE manual under "Behavioral Differentiator". (Sometimes reading manuals can be instructive...)

There are many other ways to make behavioral differentiators or integrators by using controlled sources and capacitors or inductors.

 

[srini.pes]

Thanks for your response.,
So, i need to use a opamp based differentiator to do the d/dt.

- - - Updated - - -

Thanks for your response.,
So, i need to use a opamp based differentiator to do the d/dt.

 

[FvM]

So, i need to use a opamp based differentiator to do the d/dt.

Not necessarily. A more basic behavioral circuit would use controlled sources: VCVS, capacitor, CCVS.

 

[srini.pes]

Not necessarily. A more basic behavioral circuit would use controlled sources: VCVS, capacitor, CCVS.

Sorry for the delayed reply.,

I din get what you are saying.
Can u describe it more clearly.

 

[FvM]

Input driving a VCCS, current driving a capacitor and the input of a VCVSin parallel. VCVS is used as buffer, voltage source output is the differentiated quantity. A high ohmic resistor, reset switch or .IC statement might be required to set the initial state (same thing with an OP integrator).

 

[keith1200rs]

Isn't dQ/dt = current?

Keith

 

[FvM]

Sorry, I was describing an integrator, differentiator is the other way around: VCVS as buffer, series connected capacitor, CSVS as I/V converter.

Thanks for pointing to the error.

 

[srini.pes]

Thank you so much..