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Help me with bandgap (dc simulation and tran simulation)

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godspeed.w

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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

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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

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help me about bandgap

1ms isn't enough?
 

leo_o2

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help me about bandgap

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

    godspeed.w

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godspeed.w

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help me about bandgap

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

solidstate

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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

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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

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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

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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

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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

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help me about bandgap

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

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