A voltage generating circuit comprising: an output current generating circuit, generating an output current, such that an output voltage is generated at an output terminal, according to an output voltage control signal; a comparing device, comprising a first input terminal receiving a reference voltage, a second input terminal receiving a feedback voltage related with the output voltage, and an output terminal outputting the output voltage control signal according to the reference voltage and the feedback voltage; an adjustable voltage dropping circuit, comprising a first terminal coupled to the second input terminal, and a second terminal coupled to the output terminal; and a current source, for generating a predetermined current to the first terminal of the adjustable voltage dropping circuit, thereby the feedback voltage is generated at the first terminal of the adjustable voltage dropping circuit. The predetermined current flows through the adjustable voltage dropping circuit to the output terminal.