Feedback topologies for amplifier gain reduction
AssigneepSemi Corporation
InventorsParvez DARUWALLA, Rong JIANG, Khushali SHAH
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Abstract
Feedback methods and devices to reduce gain in RF amplifiers, more in particular LNAs, are disclosed. The described methods are based on providing feedback paths from the drain terminal of one of the LNA cascode transistors to the source terminal of the LNA input transistor, or from the gate terminal of the input transistor to the source terminal of the LNA input transistor. The disclosed methods can be combined with one another or with existing feedback methods to provide further flexibility and improved tradeoffs when designing LNAs for applications having different requirements.
Claims21
(canceled)
A radio-frequency amplifier comprising:
- a cascoded gain stage including an input transistor and a cascode transistor;
- a reconfigurable network comprising switches and impedance elements arranged to form a plurality of conductive paths, each including at least one of the impedance elements, the plurality of conductive paths selectively connecting at least one of a gate node of the input transistor and a source node of the input transistor to a node of the cascode transistor.
A radio-frequency amplifier comprising:
- a multi-input front end including first and second input terminals selectively couplable to an input transistor;
- a cascoded gain stage including the input transistor in series with a cascode transistor, and
- a shared feedback network common to the first and second input terminals, the shared feedback network comprising a plurality of impedance elements and a plurality of switches arranged to be selectively connected between a node of the cascoded gain stage and a node of a selected one of the first and second input terminals.
A method of controlling gain in a radio-frequency amplifier, the method comprising:
- receiving an input signal at a gate node of an input transistor of a cascoded gain stage;
- selectively switching in and out one or more feedback connections selected from:
- (i) a connection between a drain-side node of the cascoded gain stage and the gate node of the input transistor,
- (ii) a connection between the drain-side node and a source node of the input transistor, and
- (iii) a connection between the gate node and the source node of the input transistor;
- and
- adjusting respective feedback magnitudes of any selected feedback connections.
Dependencies are inferred from the claim text.