A method and an apparatus for supplying power to a 300 PIN MSA 40Gb TRANSPONDER (22), wherein the apparatus comprises a power supply control module (21), a first resistor (R 2 ), a second resistor (R 3 ) and a third resistor (R 4 ). The power supply control module (21) supplies power to the TRANSPONDER (22) through the APS Digital pin (APS Digital) of the TRANSPONDER (22). A reference voltage terminal (V feedbaek ) of the power supply control module (21) is connected to the APS Sense pin (APS Sense) of the TRANSPONDER (22) by the second resistor (R 3 ), connected to the APS Set pin (APS Set) of the TRANSPONDER (22) by the first resistor (R 2 ) and connected to the bias voltage terminal (V bias ) of the power supply control module (21) by the third resistor (R 4 ). The method and the apparatus can increase selection of the power supply control module (21) without occupying excessive space of circuit board, while ensuring precision of supply voltage.
