Please help me out:about bandgap output

[afujian]

The output curves are showed as below after I swept the the power supply from 3v to 5v.The curves show that ,after a certain point the output value will proportionally descend while the temperature rise,why?

 

[saro_k_82]

Should be the low-supply, high-temperature supply headroom problem.
Check your bias margins in this corner.

 

[afujian]

Should be the low-supply, high-temperature supply headroom problem.
Check your bias margins in this corner.

Do you mean when the supply is low,the headroom will not be sufficient at high temperature?

 

[love_analog]

have you centered the bandgap correctly by ratioing the resistors. Ideally you want a bow tie kind of curve.
Also agree with the other poster, make sure all your transistors etc are in sat at high temp. look at opamp inputs