I am designing a close- op and bandgap, the PSRR always is very low only 60dB, But the Spec need meet 70dB. In order to increase the PSRR, I don't use Miller compensation, the capacitor are connect ground direct. Since the power voltage is 3.0V , so i can't use cascode. Who can give any devices or papers. Thanks!
PSRR is linked to output conductance of transistors as well as matching among them. Try to increase channel length of your current mirrors and increase the area of transistors in general to improve matching.
Also, actually it depends on the Vth of your transistors, 3V is high enough to accomodate cascodes. Miller compensation could also help.