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?
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