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Low-voltage differential signal driver for high-speed digital transmission

  • US 7,576,567 B2
  • Filed: 05/31/2006
  • Issued: 08/18/2009
  • Est. Priority Date: 05/31/2006
  • Status: Active Grant
First Claim
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1. A low-voltage differential signal driver for high-speed digital transmission, comprising:

  • a first current source operable to receive a signal in a first type and convert the signal into a second type, wherein the first current source comprises a set of at least two transistors and a switch associated with each transistor, the switch operable to control current flow into a gate of a transistor;

    a common-mode feedback circuit coupled to the first current source and operable to control the first current source by controlling a common-mode voltage; and

    a cascode current mirror coupled to the first current source, the cascode current mirror provides an impedance level that increases a differential output voltage and increases a voltage headroom available to output the signal, wherein the cascode current mirror comprises;

    a second current source operable to receive the signal in the second type and convert the signal into the first type, wherein the second current source comprises a first set of at least two transistors coupled in parallel with a second set of at least two transistors and a switch associated with each transistor, the switch operable to control current flow into a gate of a transistor; and

    a reference current source operable to bias a current, wherein the reference current source comprises;

    a first transistor; and

    a second transistor coupled in series with a third transistor, wherein the first and second transistors have a common terminal that goes to the first set of at least two transistors and the third transistor has a terminal that goes to the second set of at least two transistors.

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