The low value of drop out voltage in LDO

[greenhand]

Hi , every one
In some LDO datasheet , It is said that the drop out voltage is below
several hundrends or decades mV . But I think under such low
Vds or Vce , the pass transistor has fall out linear active region ,
so lost the function of regulator . Is there some one can help me?

 

[eda4you]

Re: Question about LDO

hallo greenhand,

the trick with very low dropout regulators is that a charge pump is used. This charge pump enables a gate voltage higher than vdd. So the pass transitors can be kept in linear region.