I came across some issue when I design a Bandgap Reference, which depicted in the left of the following figure. The PSRR specification required more than 70dB. When I simulate the circuit on different temperature and corners (tt, ff, ss), the value of PSRR at -40 degree is 85dB but at 115 degree is 45dB. The ripple of the PSRR is too big! How can I deal with this problem, Anabody give me some advice?
the core of circuit should be the left part, but the usual circuit uses two pnp of each edge.The better psrr can perhaps be gained by studying razavi's paper.