A power supply circuit includes an output driver transistor, a reference voltage generator circuit, an output voltage detector circuit, an amplifier circuit, and a buffer circuit. The output driver transistor outputs a current in accordance with a first control signal input thereto. The reference voltage generator circuit generates a predetermined reference voltage. The output voltage detector circuit detects an output voltage and outputs a divided voltage generated based on the output voltage. The amplifier circuit has a first polarity and a second polarity opposite to the first polarity and compares the predetermined reference voltage and the divided voltage and outputs a second control signal. The buffer circuit receives the second control signal and controls the operation of the output driver transistor in accordance with the second control signal. The buffer circuit includes first and second transistors having a polarity same as the second polarity of the amplifier circuit.