Dual-mode line driver for ethernet applications

A driver comprising:

• a first driver input;
• a second driver input;
• a first driver output;
• a second driver output;
• and
• an operational amplifier comprising:
• a first amplifier input coupled to the first driver input;
• a second amplifier input coupled to the second driver input;
• a first voltage-mode amplifier output coupled to the first driver output via a first resistor in a voltage-mode operation and coupled to the first driver output via a second resistor in a current-mode operation;
• a first current-mode amplifier output coupled to the first driver output in the current-mode operation;
• a second voltage-mode amplifier output coupled to the second driver output via a third resistor in the voltage-mode operation and coupled to the second driver output via a fourth resistor in the current-mode operation;
• and
• a second current-mode amplifier output coupled to the second driver output in the current-mode operation, wherein output current supplied by the first current-mode amplifier output and the second current-mode amplifier output is greater than output current supplied by the first voltage-mode amplifier output and the second voltage-mode amplifier output.

A system comprising:

• a digital signal processor (DSP) including an output;
• a digital-to-analog converter (DAC) including an input coupled to the output of the DSP and including first and second outputs;
• and
• a driver comprising:
• a first driver input adapted to be coupled to the first output of the DSP;
• a second driver input adapted to be coupled to the second output of the DSP;
• a first driver output;
• a second driver output;
• an operational amplifier comprising:
• a first amplifier input coupled to the first driver input;
• a second amplifier input coupled to the second driver input;
• a first amplifier output;
• a second amplifier output;
• a third amplifier output;
• and
• a fourth amplifier output, wherein output current supplied by the second amplifier output and the fourth amplifier output is greater than output current supplied by the first amplifier output and the third amplifier output;
• a first resistor;
• a first switch to selectively couple the first amplifier output to the first driver output via the first resistor;
• a second resistor;
• a second switch to selectively couple the first amplifier output to the first driver output via the second resistor;
• a third resistor;
• a third switch to selectively couple the third amplifier output to the second driver output via the third resistor;
• a fourth resistor;
• a fourth switch to selectively couple the third amplifier output to the second driver output via the fourth resistor;
• a fifth resistor;
• a fifth switch to selectively couple the first amplifier output to the third amplifier output via the fifth resistor;
• a sixth switch to selectively couple the second amplifier output to the first driver output;
• and
• a seventh switch to selectively couple the fourth amplifier output to the second driver output.

A system comprising:

• a digital signal processor (DSP) including an output;
• a digital-to-analog converter (DAC) including an input coupled to the output of the DSP and including first and second outputs;
• and
• a dual-mode driver configured for a voltage-mode operation and a current-mode operation, the driver comprising:
• a first driver input;
• a second driver input;
• a first driver output;
• a second driver output;
• an operational amplifier comprising:
• a first amplifier input coupled to the first driver input;
• a second amplifier input coupled to the second driver input;
• a first voltage-mode amplifier output coupled to the first driver output via a first resistor in the voltage-mode operation and coupled to the first driver output via the first resistor in the current-mode operation, wherein the first resistor has a first resistance value in the voltage-mode operation and has a second resistance value in the current-mode operation;
• a first current-mode amplifier output coupled to the first driver output in the current-mode operation;
• a second voltage-mode amplifier output coupled to the second driver output via a second resistor in the voltage-mode operation and coupled to the second driver output via the second resistor in the current-mode operation, wherein the second resistor has the first resistance value in the voltage-mode operation and has the second resistance value in the current-mode operation;
• and
• a second current-mode amplifier output coupled to the second driver output in the current-mode operation, wherein output current supplied by the first current-mode amplifier output and the second current-mode amplifier output is greater than output current supplied by the first voltage-mode amplifier output and the second voltage-mode amplifier output.