voltage reference ouput vary with the temp

[rock_zhu]

I used the basic reference configuration as Razavi's book. I think the normal result of ouput voltage may be like the fig"normal". The second fig is my simulation result. I tried to vary the resistor ratio but can't get the curve like "normal" one. can you tell me what's the problem? thanks

 

[eng_Semi]

It is not a wrong case, the shape depends on the temperature coefficient of the resistor, the opamp offset, and the current mirror. Ur concern should be the temperature coefficient of the reference voltage