Patent ID: 7579872

Claim:
A low-voltage differential signal driver for high-speed digital transmission, comprising: a first signal converter operable to receive a signal in a first type and convert the signal into a second type, wherein a resistance of the first signal converter is variable; a common-mode feedback circuit coupled to the first signal converter, the common-mode feedback circuit comprising an amplifier that receives an input at a terminal, wherein the input is a differential voltage measured across output nodes of the driver and the common-mode feedback circuit is operable to control the first signal converter by controlling a common-mode voltage; a second signal converter coupled to the first signal converter, the second signal converter operable to receive a signal in the second type and convert the signal into the first type, wherein a resistance of the second signal converter is variable; a current bias coupled to the second signal converter to form a cascode current mirror; wherein the first and second signal converters each comprise a first set of one or more transistors coupled in parallel with a second set of one or more transistors, and a switch associated with each of the first and second sets, the switch operable to allow and prevent current flow through the first and second sets; wherein the driver is operable to scale the resistances of the first and second signal converters to provide a constant ratio between the resistances of the first and second signal converters and differential output voltage of the driver increases according to the resistances of the first and second signal converters being scaled by reducing an overdrive voltage of the first signal converter; and wherein the cascode current mirror further increases the differential output voltage.