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LDO question about quiescent mode

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iamxo

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LDO simple question?

when the LDO is in quiescent mode, that is to say no output current is loaded.

the pass device is in subthreshold region or saturation region?

thanks all.
 

LDO simple question?

normally sub threshold
 

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    iamxo

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Re: LDO simple question?

Thank you!

Added after 34 minutes:

safwatonline said:
normally sub threshold
Click to expand...

normally?

Then, do you mean it will enter other regions in some condition?
 

LDO simple question?

When under full load, e.g. 100mA, PMOS should be on harder by decreasing the gate node voltage of PMOS output (assume it is PMOS output), then VSG is larger, and VSG-VTP > 0, and VSD always should be larger than VSDsat, so it is under saturation
When under 0 load, gate node of PMOS drives nothing and so it is trying to turn on or turn on slightly, so it can be regarded as "cut-off" region or sub-threshold region, as why sub-threshold because there is still a small amount of current flowing from PMOS to the resistive divider, so gate node is not exactly at VDD, but VDD minus some little voltages
 

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    iamxo

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Re: LDO simple question?

hung_wai_ming(at)hotmail.com said:
When under full load, e.g. 100mA, PMOS should be on harder by decreasing the gate node voltage of PMOS output (assume it is PMOS output), then VSG is larger, and VSG-VTP > 0, and VSD always should be larger than VSDsat, so it is under saturation
When under 0 load, gate node of PMOS drives nothing and so it is trying to turn on or turn on slightly, so it can be regarded as "cut-off" region or sub-threshold region, as why sub-threshold because there is still a small amount of current flowing from PMOS to the resistive divider, so gate node is not exactly at VDD, but VDD minus some little voltages
Click to expand...

O, I see, thank you very much for your reply.
 

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