In some power IC design need detect power mos Vds volt
and this volta is very small 20~30mv (Rds * current)
and who to design small volt comp ? becuase < 30mv
maybe OPA have large offset ..
and if I use series Comp hi-resolution but will low speed ..
use pnp input stage to detect voltages close to ground, use pnp level shift + pnp input stages to detect voltage < GND.
Also, pnp will inherently have low offset. Keep gain low (20-50) in first stage, then offset of second stage does not matter - probably even cmos diff amp is ok.