Why does the LDO output voltage oscillate?

The LDO regulates its output voltage using negative feedback. The output voltage oscillates when the phase of the signal to detect changes in the output voltage (VOUT) lags by 180°, turning negative feedback into positive feedback. The LDO incorporates an error amplifier, a drive circuit for an output transistor, and the output transistor. The feedback loop has an inherent delay due to the capacitance and resistance of these circuits. If the loop has a gain, negative feedback turns into positive feedback when the phase delay due to this inherent delay reaches 180°, causing the difference between the output and reference voltages to be amplified.

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