the question about VT in bandgap

[rrbice]

hi:guys!
I am new here. You can call me Robin.
recently, I have been researching this bandgap stuff.
Theoretically, Vref=Vbe+K*VT,but in simulation,the VT is not ideally PTAT.

I cannot help wondering : if the Vt is not ideally PTAT,how am I supposed to get an parabolic curve as the book tell us?
Further, Vt is not a PTAT ideally voltage, is it possible to get a temperature compensation?

Is this all because the model of Vbe?

thanks in advance!

 

[leo_o2]

Yes, you can have the compensation with non-ideal PTAT VT. Process is not exactly same.

 

[rrbice]

thanks，leo.
but the problem is if the Vptat is not ideally PTAT, how am I supposed to get the theoretical convex curve?
Further more ,how to compensate the Vtln(T/T0) if the Vptat itself is not ideal?

 

[nus_lin]

the error sources that cause nonideal ptat behavior is by beta, finite base impedance. normally a beta is properly modeled in the design kit, but base impedance is not. you may keep the current density low to minimize its effect.