Is it possible to do a AC simulation for a switching circuit?

[sgharagoz]

Just wondering if it is possible to do AC simulation when part of the circuit has digital gates in it?

If not could you tell me why?

Cheers

 

[keith1200rs]

It depends on what the gates do. At best you will get an AC analysis for the circuit with the gates in one state.

An AC analysis finds a static DC operating point first and assumes that doesn't change. It then calculates the small signal transfer function at that DC operating point only.

Keith

 

[sgharagoz]

Thanks Keith

I have a switching circuit controlling the current sink of an Op-Amp. Of course during the time when the gates are turing on and Off Op-Amp doesn't work once everything is steady Op-Amp operates.

I tried this HSPICE but gain were not right!

Cheers

 

[LvW]

Thanks Keith

I have a switching circuit controlling the current sink of an Op-Amp. Of course during the time when the gates are turing on and Off Op-Amp doesn't work once everything is steady Op-Amp operates.

I tried this HSPICE but gain were not right!

Cheers

Suggestion: Perhaps two succeeding ac simulations (for both switch positions) can give you some information.
In both cases, the restrictions as mentioned by Keith apply (small signal behaviour for a fixed dc operating point).

 

[sgharagoz]

My problem is more severe than that!

I have to do monte carlo simulations to check the intra-die variations! So every time I run the monte Carlo it generates a new set of variable which makes my life more miserable!

 

[LvW]

I have to do monte carlo simulations
to check the intra-die variations!
So every time I run the monte Carlo it generates a new set of variable
which makes my life more miserable!

At least, you deserve a price for being the first individuum in this forum who has put his question in form of a poem.
Congratulation!

 

[sgharagoz]

Lol,

I have to work on that to make it rhythm better!

 

[lamoun]

I THINK that you can use PAC analysis. (I haven't used it before)
Take a look here
https://www.designers-guide.org/analysis/sc-filters.pdf

Monte carlo uses the same variations for each iteration of different runs.
That is, if you run the same circuit twice, each iteration of both runs will give you the same result.

it1.run1=it1.run2
it2.run1=it2.run2
it3.run1=it3.run2
.
.

...at least running Monte Carlo in cadence ADE with Spectre simulator

 

[erikl]

Just wondering if it is possible to do AC simulation when part of the circuit has digital gates in it?

You can perhaps use PAC analysis:

 

[sgharagoz]

I try to explain my problem better!
I have two files each has an opamp in it! they are identical.

If I run AC Monte carlo simulation for the first file can I use the exact variations to do a monte carlo simulation for the second file?

Thanks a lot for all your suggestions!