The common voltage generator includes an operational amplifier and a plurality of switches. The operational amplifier is configured to amplify a difference between a first voltage and a second voltage and to output the amplified voltage as a common voltage. The plurality of switches are configured to transmit a third voltage and a fourth voltage as a power supply to the operational amplifier in a first voltage output mode and to transmit a fifth voltage and a sixth voltage as a power supply to the operational amplifier in a second voltage output mode.