Help me with bandgap (dc simulation and tran simulation)

[godspeed.w]

help me about bandgap

I sweep temperature from -40 to 80 and find that the voltage range of bandgap output is about 2mv .
but when I do tran simulation at the same time sweep temperature from -40 to 80 ,the result is that the voltage range of bandgap output is about 20mv.
why the result of dc simulation is different with tran simulation?
the current of collector is 5uA.

 

[poseidonpid]

Re: help me about bandgap

.dc is a stable scan, and .tran is a transient scan, if .tran time is large enough,the
result will be close with .dc scan.

 

[godspeed.w]

help me about bandgap

1ms isn't enough?

 

[leo_o2]

help me about bandgap

It is strange. Any difference for conditions like VIN and process corner?

 

[godspeed.w]

help me about bandgap

I can't find the reason of it who can help me .
thanks!

 

[solidstate]

help me about bandgap

Are you doing a DC analysis with a temperature sweep or a parametric analysis over temperature? I would suggest doing the latter..

 

[godspeed.w]

help me about bandgap

1) .dc temp -40 80 5
2) .tran 1n 10u 1n sweep temp -40 80 5

this two result is different.
what is parametric analysis over temperature?

 

[solidstate]

help me about bandgap

What kind of simulation environment are you using?
I was suspecting that the dc simulation computes an operating point and uses some linearized model in the temperature sweep, while the transient simulation might calculate a dc operating point for every transient step, and that the difference would be coming from that. Is such a thing possible with your current setup?

 

[godspeed.w]

help me about bandgap

hspice.
transient simulation compute based on the the dc value .
what kind of simulaiton do you do about temp sweep .

 

[PaloAlto]

help me about bandgap

For temperature, I either do DC sweep or parametric anlysis changing temp. That's simply doing several DC analysis each with different temp

I've never done such thing as tran with temp sweep, I don't know what you can get there

 

[leo_o2]

help me about bandgap

Yes, I never used sweep for tran. Usually alter is used to changed parameter temp.

 

[godspeed.w]

help me about bandgap