Patent ID: 7173401

Claim:
A low drop-out (LDO) regulator, comprising: a differential amplifier circuit having a positive input terminal, a negative input terminal, an output terminal, a bias terminal and a ground terminal, comprising: a differential pair circuit electrically coupled to the negative input terminal and the output terminal, receiving an input voltage from the positive input terminal, and electrically coupled to a positive bias through the bias terminal; a current source for providing a constant current; a current mirror circuit for receiving the constant current and mirroring the constant current to the differential pair circuit, and the current mirror circuit being grounded through the ground terminal; and a first PMOS transistor having a first source/drain terminal electrically coupled to the current mirror circuit for receiving the constant current, a second source/drain terminal electrically coupled to the positive bias through the bias terminal, and a gate electrically coupled to the output terminal; a first passive element having a first terminal being grounded, and a second terminal electrically coupled to the negative input terminal; and a second PMOS transistor having a first source/drain terminal electrically coupled to the negative input terminal and the second terminal of the first passive element, a gate electrically coupled to the output terminal, and a second source/drain terminal electrically coupled to the positive bias.