question about bandgap reference

[joehwang]

Hi, I got some questions about the bandgap reference:

1. what is gm-based reference? Is it constant-gm biasing?
2. In the fig.1, why the output of the op-amp (node P) can adjust the gate voltage of the PMOS devices so as to "Equalize" Vx = Vy?
3. Also in the fig.1, what will happen if I change the input polarity of the op-amp? Does the polarity matter with the stable issue?

Thanks!

Wang

 

[keoiuser]

hi,
i just want to say that when i designed a bandgap, if i connecte the ampli output to the pmos gates, i could not have a good stability. I connected the pmos gates to a startup circuit