Gain Invariant Impedance Feedback Amplifier
AssigneeBroadcom Corporation
InventorsGiuseppe Cusmai, Vijayaramalingam Periasamy, Xi Chen, Ramon Alejandro Gomez
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Abstract
A system includes a weighting element, a transconductance circuit, a feedback loop, and an auxiliary loop. In some implementations, the transconductance circuit may accept an input and provide a first portion of an output for amplification at a variable amplification level to generate an amplifier output. The feedback loop may provide a portion of the amplifier output as a first feedback to the input. The first feedback may be associated with an impedance that may vary with the amplification level. The auxiliary loop may provide a second feedback to the input to reduce the dependence of the impedance on the amplification level.
Claims20
A system, comprising:
- an transconductance circuit comprising an input and a first output;
- a weighting element coupled to the first output, the weighting element comprising:
- a first path configured to produce an amplifier output responsive to the first output;
- and
- a second path configured to split off an auxiliary portion of the first output;
- a feedback loop comprising an amplification level dependent impedance, the feedback loop configured to provide a first portion of the amplifier output as a first feedback to the input;
- and
- an auxiliary loop configured to:
- accept the auxiliary portion of the first output;
- and
- reduce dependence of the impedance on the amplification level by providing, to the input, an amplification level dependent feedback responsive to the auxiliary portion.
A method, comprising:
- amplifying a first portion of an first output to generate an amplifier output, the amplifier output related to an input by an amplification level;
- providing, via a feedback loop, a portion of the amplifier output as a first feedback to the input;
- varying a first magnitude of the amplifier output in proportion to the amplification level;
- providing, via an auxiliary loop, auxiliary portion of the first output as a second feedback to the input;
- and
- varying a second magnitude of the second feedback inversely to the amplification level.
A device, comprising:
- an transconductance circuit comprising:
- an input at a first terminal of a transconductance transistor,
- a resistor situated between a ground and a second terminal of the transconductance transistor;
- and
- a first output at a third terminal of the transconductance transistor, a current between the ground and first output configured to be controlled via the input;
- a weighting element comprising:
- a first transistor, over which a first portion of the first output traverses, the first transistor comprising a first number of finger elements, the first transistor configured to amplify the first portion to generate an amplifier output, the input being related to the amplifier output by an amplification level;
- a second transistor over which a second portion of the first output traverses, the second transistor comprising a second number of finger elements, a difference between the first and second numbers being equal to a third number, a relationship between a first portion magnitude and a second portion magnitude being dependent on the amplification level;
- a third transistor over which an auxiliary portion of the first output traverses, the third transistor comprising the third number of finger elements;
- and
- a feedback loop configured to provide a portion of the amplifier output across a resistor to serve as a first feedback to the input;
- and
- an auxiliary loop comprising:
- a path configured to provide a second feedback to the input responsive to the auxiliary portion, the third transistor configured to vary a second feedback magnitude inversely to the amplification level.
Dependencies are inferred from the claim text.