Automatic gain control loop
First Claim
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1. An optical receiver comprising:
- a photodetector for converting an input optical signal into an input electrical current signal;
a transimpedance amplifier (TIA) for converting the input electrical current signal into an input voltage signal, the TIA including a feedback resistor RF and a variable gain feed-forward amplifier for generating a feed forward gain Ao;
a gain amplifier for amplifying the input voltage signal to a desired voltage level; and
an automatic gain control loop for generating at least one gain control signal capable of varying the value of the feedback resistor RF and the feed forward gain Ao of the variable gain feed-forward amplifier.
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Abstract
In conventional optical receivers the dynamic range is obtained by using variable gain amplifiers (VGA) with a fixed trans-impedance amplifier (TIA) gain. To overcome the SNR problems inherent in conventional receivers an improved optical receiver comprises an automatic gain control loop for generating at least one gain control signal for controlling gain of both the VGA and the TIA. Ideally, both the resistance and the gain of the TIA are controlled by a gain control signal.
9 Citations
14 Claims
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1. An optical receiver comprising:
- a photodetector for converting an input optical signal into an input electrical current signal;
a transimpedance amplifier (TIA) for converting the input electrical current signal into an input voltage signal, the TIA including a feedback resistor RF and a variable gain feed-forward amplifier for generating a feed forward gain Ao;
a gain amplifier for amplifying the input voltage signal to a desired voltage level; and
an automatic gain control loop for generating at least one gain control signal capable of varying the value of the feedback resistor RF and the feed forward gain Ao of the variable gain feed-forward amplifier. - View Dependent Claims (2, 3, 5, 7, 8, 9, 10, 11, 12, 13, 14)
- a photodetector for converting an input optical signal into an input electrical current signal;
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4. An optical receiver comprising:
- a photodetector for converting an input optical signal into an input electrical current signal;
a transimpedance amplifier (TIA) for converting the input electrical current signal into an input voltage signal, the TIA including a feedback resistor;
a gain amplifier for amplifying the input voltage signal to a desired voltage level; and
an automatic gain control loop for generating a first gain control signal capable of varying a value of the feedback resistor and feed forward gain of the variable gain feed-forward amplifier;
wherein the feedback resistor Rr comprises a control transistor connected in parallel with a fixed feedback resistor;
wherein the automatic gain control loop is capable of applying the first gain control signal to a gate of the control transistor to control the fixed feedback resistor.
- a photodetector for converting an input optical signal into an input electrical current signal;
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6. An optical receiver comprising:
- a photodetector for converting an input optical signal into an input electrical current signal;
a transimpedance amplifier (TIA) for converting the input electrical current signal into an input voltage signal, the TIA including a feedback resistor and a variable gain feed-forward amplifier;
a gain amplifier for amplifying the input voltage signal to a desired voltage level; and
an automatic gain control loop for generating a first gain control signal for varying at least one of a resistance value of the feedback resistor and feed forward gain of the variable gain feed-forward amplifier;
wherein the automatic gain control loop includes;
a peak detector capable of measuring an amplitude of an output voltage signal from the gain amplifier; and
an amplifier capable of comparing the amplitude of the output voltage signal with a reference voltage, wherein the first gain control signal is based at least in part on the comparison between the amplitude of the output voltage signal and the reference voltage.
- a photodetector for converting an input optical signal into an input electrical current signal;
Specification