A source driver for an LCD panel includes two gm stages and two output buffers. In a normal operation mode, the first gm stage and the first output buffer establish a unity gain buffer to amplify a positive polarity analog voltage to be a positive polarity output voltage, and the second gm stage and the second output buffer establish a unity gain buffer to amplify a negative polarity analog voltage to be a negative polarity output voltage. In a polarity inversion mode, the second gm stage and the first output buffer establish a unity gain buffer to amplify a positive polarity analog voltage to be a positive polarity output voltage, and the first gm stage and the second output buffer establish a unity gain buffer to amplify a negative polarity analog voltage to be a negative polarity output voltage.