Preemphasis driver with replica bias
First Claim
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1. A system comprising:
- a low-frequency-period replica driver that comprises a plurality of n-type digital-to-analog converter (NDAC) current sources, the replica driver being operable to produce a low-frequency-period reference voltage based on current supplied by the NDAC current sources, wherein the replica driver further comprises a plurality of switches that are operable to selectively couple one of the NDAC current sources to a low-output voltage (VOL) node or a high-output voltage (VOH) node of the replica driver;
a peak-output-voltage replica driver that comprises another plurality of NDAC current sources, the peak-output-voltage replica driver being operable to produce a peak-output-voltage reference voltage based on current supplied by the other NDAC current sources; and
a plurality of driver fingers that are coupled to the replica driver and each comprise a driver bias circuit and an output driver, the driver bias circuit comprising an operational amplifier (op-amp) that is operable to adjust current-source gate voltage in the output driver to produce voltages at output nodes of the driver fingers that approximately match the reference voltage produced by the replica driver, each one of the driver bias circuits comprising a switch that is operable to selectively couple an input of the op-amp in the driver bias circuit to the low-frequency-period reference voltage or the peak-output-voltage reference voltage.
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Abstract
In one embodiment, a system includes a replica driver that includes n-type digital-to-analog converter (NDAC) current sources. The replica driver can produce a reference voltage based on current supplied by the NDAC current sources. The system includes driver fingers that are coupled to the replica driver and each include a driver bias circuit and an output driver. The driver bias circuit includes an operational amplifier (op-amp) that can adjust current-source gate voltage in the output driver to produce voltages at output nodes of the driver fingers that approximately match the reference voltage produced by the replica driver.
32 Citations
18 Claims
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1. A system comprising:
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a low-frequency-period replica driver that comprises a plurality of n-type digital-to-analog converter (NDAC) current sources, the replica driver being operable to produce a low-frequency-period reference voltage based on current supplied by the NDAC current sources, wherein the replica driver further comprises a plurality of switches that are operable to selectively couple one of the NDAC current sources to a low-output voltage (VOL) node or a high-output voltage (VOH) node of the replica driver; a peak-output-voltage replica driver that comprises another plurality of NDAC current sources, the peak-output-voltage replica driver being operable to produce a peak-output-voltage reference voltage based on current supplied by the other NDAC current sources; and a plurality of driver fingers that are coupled to the replica driver and each comprise a driver bias circuit and an output driver, the driver bias circuit comprising an operational amplifier (op-amp) that is operable to adjust current-source gate voltage in the output driver to produce voltages at output nodes of the driver fingers that approximately match the reference voltage produced by the replica driver, each one of the driver bias circuits comprising a switch that is operable to selectively couple an input of the op-amp in the driver bias circuit to the low-frequency-period reference voltage or the peak-output-voltage reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method comprising:
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by a low-frequency-period replica driver that comprises a plurality of n-type digital-to-analog converter (NDAC) current sources, producing a low-frequency-period reference voltage based on current supplied by the NDAC current sources; by a plurality of switches in the replica driver, selectively coupling one of the NDAC current sources to a low-output voltage (VOL) node or a high-output voltage (VOH) node of the replica driver; by an operational amplifier (op-amp) in a driver bias circuit in each of a plurality of driver fingers that are coupled to the replica driver, adjusting current-source gate voltage in the output driver to produce voltages at output nodes of the driver fingers that approximately match the reference voltage produced by the replica driver; by a peak-output-voltage replica driver that comprises another plurality of NDAC current sources, producing a peak-output-voltage reference voltage based on current supplied by the other NDAC current sources; by a switch in each one of the driver bias circuits, selectively coupling an input of the op-amp in the driver bias circuit to the low-frequency-period reference voltage or the peak-output-voltage reference voltage. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification