How to use an ac command?

[ampper]

The chip has a soft-start and some blocks need time to strat-up .
if i run an ac simulation,the chip does not work and the result is wrong.
So,how to have an ac simulation when the chip is working .


Thanks for your help!

 

[renwl]

The chip has a soft-start and some blocks need time to strat-up .
if i run an ac simulation,the chip does not work and the result is wrong.
So,how to have an ac simulation when the chip is working .


Thanks for your help!

if ac simulation can not simulate soft-start , why not remove it and replace it with ideal block?

 

[safwatonline]

u can set initial conditions that represent steady state

 

[ampper]

Thanks！

I replace the soft-start block with a steady state,but i am not sure whether the ac simulation result is right or not.

Can have ac simulation when block have a start-up circuit?

The start-up time is about 1ms

 

[renwl]

i think the soft-start is time domain function. however ac is the frequency domain.
ac can not simulate soft-start.

 

[swkimaz]

For AC analysis, first find bias point of your circuit and use them for your AC simulation because bias points in your circuit will not be changed for AC analysis.

 

[Areky_qin]

set working dc poit for ur ac simulation initial conditios.

 

[paji]

remove the soft-start block

Added after 1 minutes:

or you can set the input of soft-start of the opa to VDD