A gamma voltage generator, a source driver and a display apparatus are provided. The gamma voltage generator includes a gamma voltage generating circuit and a plurality of buffers. The gamma voltage generating circuit has a plurality of voltage input end nodes and a plurality of voltage output end nodes for outputting the predetermined number of gamma voltages based on input voltages from the plurality of voltage input end nodes. Each buffer has an input end receive a corresponding gamma reference voltage, and an output end coupled to a corresponding voltage input end node. The gamma voltage generating circuit includes multiple resistor units connected in series, and each resistor unit is configured to have a second resistance value when operating in the second mode less than a first resistance value when operating in the first mode.