Low supply voltage differential signal driver

A differential signal driver comprising:

• means for providing a voltage source;
• means for providing a current source;
• two differential current steering transistor legs to drive a signal, each leg including at least two transistors coupled in series, one end of each leg coupled to the voltage source means and the other end of each leg coupled to the current source means, the output for each leg measured where the at least two transistors intersect;
• and
• means for adjusting the driver's common-mode voltage to the level of a target common-mode voltage;
• wherein said current source comprises:
• a fixed current source to provide a fixed current;
• and
• a second current source to provide a variable current, the variable current to vary according to the means for adjusting the driver's common-mode voltage;
• wherein the second current includes a plurality of conducting legs, each current conducting leg individually configurable to provide a desired current.

A method comprising:

• measuring a common-mode voltage of a differential signaling driver circuit, the differential signaling driver circuit including a plurality of current steering transistor legs, each transistor leg including a first transistor coupled to a voltage source;
• operating each first transistor in a plurality of current steering transistor legs as a voltage-controlled resistor;
• comparing the driver's common-mode voltage to a target common-mode voltage level;
• and
• adjusting the driver's total direct current (DC) to bring the driver's common-mode voltage to the same level as the target common-mode voltage, wherein adjusting the driver's total direct current (DC) comprises:
• providing a first current source to provide a fixed current;
• and
• providing a second current source to provide a variable current, the variable current being controlled to adjust the driver's common-mode voltage, wherein the second current source includes a plurality of current conducting legs, each current conducting leg individually configurable to provide a desired current.

A method comprising:

• measuring a common-mode voltage of a differential signaling driver circuit, the differential signaling driver circuit including a plurality of current steering transistor legs, each transistor leg including a first transistor coupled to a voltage source;
• operating each first transistor in a plurality of current steering transistor legs as a voltage-controlled resistor;
• comparing the driver's common-mode voltage to a target common-mode voltage;
• and
• adjusting the resistance of the driver circuit, while keeping the driver's total direct current (DC) fixed, to bring the driver's common-mode voltage to substantially the same level as the 10 target common-mode voltage, wherein adjusting the driver's total direct current (DC) comprises:
• providing a first current source to provide a fixed current;
• and
• providing a second current source to provide a variable current, the variable current being controlled to adjust the driver's common-mode voltage, wherein the second current source includes a plurality of current conducting legs, each current conducting leg individually configurable to provide a desired current.