Quote:since the bg is generating a reference current, you have to look the power supply sensitivity of the output current, not the voltage.
I think newic was chiefly concerned with BGR voltage PSR, not the current because current PSR is itself very good.
Quote:considering any small-signal variation at the opamp output as an noise source of the PMOS transistor, increasing gm actually enlarge the current noise. if you want to have a high loop gain, it can only be done by by enhancing the opamp gain.
As far as PSR is concerned, I beg to differ. We want the PSR at opamp output to be very low. We want exactly the same variation at opamp output as it occurs at VDD, so as to keep the VGS of the PMOS same, & hence the same current.
Noise current increases with increasing gm, but that's not what he was talking abt.
Quote:furthermore, even for the voltage PSRR, having larger gm without increasing the transistor size might also not help, because you reduce the voltage headroom, thus get a smaller rout.
Same explanation as above. Also, larger the transistor size, better the CGS, better the high freq. PSR.
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Mayank.