Evaluate my PTAT current source

[lhlbluesky]

i have designed a ptat current source,the Vref=1.239V,TC=10ppm(tt)\38ppm(ff)
the change of Vref is 3mV(tt)\7mV(ff) when VDD is 1.62-1.98V;
is that ok?
how's a good ptat current source?what's the Tc and change rate of Vref with VDD,
besides,how to improve the PSRR and TC simultaneously?what's the effect of the area of the two transistors ?
i'm confused , please help me.

 

[stoned]

bandgap problem

In my opinion
Vref change with VDD is vrey little, only about several mV.
and Tc should not change.
boost the gain of amplifier can improve the PSRR, improve TC should cancel the 2rd temperature feature of resistor.
Two transistor? Bipolar? 8:1 is fine for layout

 

[fjord]

bandgap problem

I think that for TC=10ppm you should use quadratic PTAT current generator. Design of quadratic PTAT is most difficult but you will have better TC.