Small-area and ultralow-noise LDO

The invention belongs to the field of power management and particularly relates to a small-area and ultralow-noise LDO. The LDO comprises a fore-stage pre-regulation module and a post-stage regulation module. The fore-stage pre-regulation module comprises an error amplifier, a resistance potential-divider network and an RC low-pass filter, wherein the error amplifier, the resistance potential-divider network and the RC low-pass filter are connected in sequence. The post-stage regulation module comprises a post-stage error amplifier and a PMOS pass transistor. The output of the fore-stage pre-regulation module is connected with the input of the post-stage regulation module, and the input of the post-stage regulation module is connected with a load current source. According to the LDO, it can be guaranteed that a low-pass filter circuit has very low cut-off frequency just through very small capacitance to filter out noise produced by a reference voltage source, and voltage obtained after conversion can be output with ultralow noise; meanwhile, the area of a chip is greatly reduced and the noise performance of the circuit is greatly improved; furthermore, a high power supply rejection ratio can be achieved.