A power supply circuit includes a first transistor and a second transistor electrically coupled between a power supply terminal and an output terminal. When a first current path, in which output terminal through the first transistor, is formed, a voltage level of the output terminal may be controlled to be greater than or equal to a predetermined level. When a second current path, in which a current flows from the power supply terminal to the output terminal through the second transistor, is formed, the voltage level of the output terminal may be controlled to be less than or equal to the predetermined level.