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I actually mean f0dB of the open loop gain of a LDO. And I borrowed the term GBW from amplifier.
Here is what I think: although LDO is not a amplifier to amplify signal, it does act like a amplifier to reject supply noise or transient load dump. So I guess these performance will be related to the f0dB of a LDO.
For this purpose, you have to consider the reference voltage (usually half of the output voltage) as input for a control loop and the varying input voltage as a disturbing parameter.
Then, the control loop has to ensure that the output voltage follows the reference. Therefore the closed loop has a gain of "two". A model of this loop looks as follows:
All parts (opamp, path element) are in the forward path - except the resistive voltage divider (as mentioned: usually 0.5) which is in the feedback path beween Vout and the input unit that subtracts the feedback voltage from the reference.
This is a good starting point to measure/compute/simulate the loop gain and to identify the unity gain frequency.
qslzaio,hello!The closed loop GBW can be caculated from the time you want Vout to settle to a certain value within some settling error,for ex, 1%.Just like the way in which we design the OTA's GBW in ADC design.
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