Help!How to drcrease the rapple of PSRR in bandgap referene

[dasong]

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?

 

[watersky]

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.

 

[APPLESTREE]

Re: Help!How to drcrease the rapple of PSRR in bandgap refer

I am wondering how you measure the PSRR?

why did you use a resistor at the output port? The two PMOS(at the output branch) works fine?

 

[itheman]

Re: Help!How to drcrease the rapple of PSRR in bandgap refer

Hi,

Put a big CAP between the top PMOS bia node and the supply. This will give you a very good AC PSRR. Get back to the board with the results