How to decrease the variation of bandgap output voltage?

[flushrat]

For a conventional bandgap, if sweep temperature from -40 to 120, the bandgap output voltage is like this. In the figure, the max V is 1.206V at 35℃, the min V is 1.199V at 120℃. My question is how to decrease this variation?

Vout=Vbe+△Vbe*R2/R1=Vbe+kT/q*ln*R2/R1

Which factor will affect the variation? n or the value of R1 or others?

 

[erikl]

See e.g. this paper: View attachment A Design Methodology for Matching Improvement in Bandgap References - isqed07juan.pdf

 

[love_analog]

Sorry erikl, I tend to disagree. The paper seems to talk about matching. The OP has done everything. The tempco is zero at ~center. I think the only thing he can do is curvature compensation. Extra trimming etc. won't make anything better.