Analog amplifier having DC offset cancellation circuit and method of offset cancellation for analog amplifiers
AssigneeAgere Systems Inc.
InventorsJinghong Chen, Gregory W. Sheets, Joseph Anidjar, Robert J. Kapuschinsky, Lane A. Smith
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Abstract
An amplifier having DC offset compensation includes at least one input node and a pair of differential output nodes, a biasing circuit coupled to the input node; and a plurality of current sources. Selected ones of said current sources are coupled to the input node to adjust a DC voltage at the input node to provide DC offset compensation for the amplifier
Claims14
An amplifier having DC offset compensation, said amplifier comprising:
- a pair of differential input nodes and a pair of differential output nodes;
- first and second biasing circuits coupled to said input nodes;
- and
- a plurality of binary weighted selectable current sources, said plurality of binary weighted selectable current sources comprising a first group of selectable current sources associated with a first one of said differential input nodes comprising at least one selectable current source and a second group of selectable current sources associated with a second one of said differential input nodes comprising at least one selectable current source, wherein selected ones of said current sources are coupled to said input nodes to adjust a respective DC voltage at each of said input nodes to simultaneously provide DC offset compensation for said amplifier.
An amplifier having DC offset compensation, said amplifier comprising:
- a pair of differential input nodes and a pair of differential output nodes;
- a biasing circuit coupled to said input nodes, said biasing circuit providing a positive default bias at said inputs nodes;
- and
- means for simultaneously adjusting a DC voltage at each of said input nodes from said positive default bias to provide DC offset compensation for said amplifier in accordance with a programmed DC offset.
A calibration system for an amplifier having a DC offset, said amplifier comprising at least one input node, a pair of differential output nodes and an offset compensation adjustment circuit responsive to a control signal to adjust a DC voltage at said input to provide DC offset compensation for said amplifier, wherein said offset compensation adjustment circuit comprises a plurality of selectable current sources, selected ones of said current sources being selected for coupling to said input node of said amplifier by said control signal to adjust said DC voltage at said input to provide said DC offset compensation for said amplifier, said system comprising:
- an offset detection module having a pair of inputs corresponding to said output nodes, said offset detection module providing an offset detection output representative of said DC offset;
- and
- an offset compensation control module for providing the control signal to said offset compensation adjustment circuit for adjusting said DC offset, wherein said amplifier is formed in an integrated circuit and said offset compensation control module is external to said integrated circuit, wherein the control signal programs the DC offset into said integrated circuit.
A method of compensation for DC offset in an amplifier, said amplifier comprising a pair of differential input nodes and a pair of differential output nodes, comprising the steps of:
- selectively coupling a plurality of current sources simultaneously to said input nodes in a combination that adjusts a DC voltage at said input nodes to provide DC offset compensation for said amplifier.
Dependencies are inferred from the claim text.