Patent ID: 7075977

Claim:
A driving circuit of a transceiver output port of a local area networking device, wherein the transceiver output port is coupled to a cable and the driving circuit is for outputting a differential output signal to the cable, the driving circuit comprising: a first output node; a second output node, wherein the first and second output nodes are for outputting the differential output signal; a first current source coupled to the first output node for providing a first current; a second current source coupled to the second output node for providing a second current; a first resistor coupled to the first output node; a second resistor coupled to the second output node; a third current source coupled between the first output node and a supply voltage source for providing a third current; and a fourth current source coupled between the second output node and the supply voltage source for providing a fourth current; wherein the resistance of the first resistor and the resistance of the second resistor each are equal to Â½ of the equivalent resistance of the cable for the purpose of impedance matching to the cable, and wherein the third and fourth current sources are used for providing currents while the first and second current sources are operating such that the magnitude of the differential output signal is determined not only according to the first and second currents but also according to the third and fourth currents.