Weighted multi-input variable gain amplifier
First Claim
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1. A loss of signal (LOS) detection circuit, comprising:
- a plurality of detectors to detect a signal from a plurality of sampling points in an amplifier chain;
a plurality of differential amplifiers for amplifying outputs of said plurality of detectors;
an adder to add outputs of said plurality of differential amplifiers; and
a comparator to compare an output of said adder to a threshold value and output an LOS alarm signal if said output of said adder is below said threshold value.
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Abstract
A limiting amplifier (LIA), used for example in high speed optical communication systems, includes a loss of signal (LOS) feature that may provide improved optical receiver performance and includes wide range user-programmable thresholds for generating analog loss of signal (LOS) alarms. In particular, multiple sampling points within the limiting amplifier may be used. These samples may be differentially amplified with weighted gains and then combined and compared to a threshold value to generate an LOS alarm signal.
48 Citations
29 Claims
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1. A loss of signal (LOS) detection circuit, comprising:
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a plurality of detectors to detect a signal from a plurality of sampling points in an amplifier chain;
a plurality of differential amplifiers for amplifying outputs of said plurality of detectors;
an adder to add outputs of said plurality of differential amplifiers; and
a comparator to compare an output of said adder to a threshold value and output an LOS alarm signal if said output of said adder is below said threshold value. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A limiting amplifier (LIA) having a loss of signal (LOS) circuit, comprising:
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a plurality of amplifier stages connected in series to progressively amplify an input signal;
a plurality of sampling points after ones of said plurality of amplifier stages;
a plurality of peak detectors each connected to one of said plurality of sampling points;
a plurality of differential amplifiers each connected to receive an output from one of said plurality of peak detectors;
a circuit to combine an output from each of said plurality of differential amplifiers to output a combined signal; and
a comparator to output a LOS alarm signal if said combined signal is below a threshold value. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method for generating a loss of signal (LOS) alarm signal, comprising:
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sampling a signal at a plurality of sampling points after each of a plurality of amplifier stages;
differentially amplifying sampled signals;
combining said differentially amplified signals to produce a combined signal; and
outputting an LOS alarm signal if said combined signal is below a threshold value. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. An amplifier circuit, comprising:
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a plurality inputs to receive a plurality of sampled signals;
a plurality of differential amplifiers each connected to one of said plurality of inputs, and an adder to add a signal output from each of said plurality of differential amplifiers to produce a combined signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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Specification