A power source circuit of a display apparatus includes a voltage divider, an operational amplifier, a first switch, a second switch, and a protector. The voltage divider generates a divided voltage between a first driving voltage and a ground voltage. The operational amplifier receives the divided voltage and outputs the divided voltage as a second driving voltage. The first switch is connected between a first supply voltage terminal to receive the first driving voltage and a common node. The second switch is connected between the common node and a second supply voltage terminal to receive the ground voltage. The protector is connected to the common node to limit a voltage output of the first supply voltage terminal in response to a voltage of the common node.