Techniques for improving amplifier linearity
AssigneeQUALCOMM Incorporated
InventorsXiaoyong Li, Sang-Oh Lee, Cormac S. Conroy
Life of this patent
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Abstract
Techniques for improving the linearity of a cascode amplifier. In an exemplary embodiment, an auxiliary common-gate amplifier is provided in parallel with the principal cascode branch. The auxiliary common-gate amplifier samples a cascoded node in the principal cascode branch. The auxiliary common-gate amplifier generates a current which, when combined with the current generated by the principal cascode branch, cancels a distortion component to generate an output current with improved linearity characteristics. In an exemplary embodiment, a phase shifting network couples the cascoded node to the auxiliary common-gate amplifier, and may include, e.g., a capacitor coupled to an inductor.
Claims15
A method for improving the linearity of a cascode amplifier, method comprising:
- accepting an input voltage;
- generating a principal cascode current based on the input voltage;
- coupling a signal at a cascoded node of the amplifier to the source of a common-gate amplifier via a phase shifting network;
- generating an auxiliary cascode current using the common-gate amplifier;
- biasing the common-gate amplifier to cancel a distortion component in the principal cascode current;
- and
- combining the auxiliary cascode current with the principal cascode current to generate an output current of the cascode amplifier.
A cascode amplifier apparatus having improved linearity, the apparatus comprising:
- a first principal transistor and a second principal transistor coupled in a cascode configuration, the first and second principal transistors forming a principal cascode branch, the principal cascode branch having an output and a cascoded node;
- a phase shifting network coupled to the cascoded node;
- and
- a common-gate amplifier having an input coupled to the output of the phase shifting network, the output of the common-gate amplifier coupled to the output of the principal cascode branch.
A cascode amplifier apparatus having improved linearity, the apparatus accepting an input voltage, the apparatus comprising:
- means for generating a principal cascode current based on the input voltage;
- means for generating an auxiliary cascode current, the auxiliary cascode current coupled to the principal cascode current to generate an output current;
- and
- means for coupling a signal at a cascoded node of the amplifier to the means for generating an auxiliary cascode current.
Dependencies are inferred from the claim text.