Optical receiver using variable negative-capacitance circuit
AssigneesHitachi, Ltd., Hitachi Device Engineering Co., Ltd.
InventorsToru Masuda, Katsuyoshi Washio, Taizo Yoshikawa, Eiji Ohue, Kenichi Ohhata
Life of this patent
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Abstract
A large time constant is caused due to parasitic capacitance at an anode terminal of a photodetector of an optical receiver. Therefore, an optical receiver wherein a variable negative capacitor mainly including an NPN-type transistor operable at high speed is configured and is connected to the input terminal of a preamplifier to which the output of the photodetector is input so that parasitic capacitance caused in the photodetector and due to packaging is equivalently reduced and the fluctuation of parasitic capacitance caused due to manufacturing dispersion is also compensated is provided.
Claims19
An optical receiver, comprising:
- a photodetector to which an optical modulated signal is input and which outputs photoelectric current;
- a preamplifier the input terminal of which is connected to an anode terminal of the photodetector, which converts a current signal to a voltage signal and outputs the voltage signal;
- an automatic gain controllable amplifier that keeps the amplitude of the voltage signal output from the preamplifier at a predetermined value;
- means for processing a signal output from the automatic gain controllable amplifier and acquiring predetermined digitalized electric information;
- and
- a variable negative capacitor connected to the anode terminal of the photodetector, wherein:
- the variable negative capacitor generates negative capacitance at the input terminal of the preamplifier and the quantity of the negative capacitance is variable according to a control voltage.
An optical receiver, comprising:
- a photodetector to which an optical modulated signal is input and which outputs photoelectric current;
- a preamplifier the input terminal of which is connected to an anode terminal of the photodetector, which converts a current signal to a voltage signal and outputs the voltage signal;
- an automatic gain controllable amplifier that keeps the amplitude of the voltage signal output from the preamplifier at a predetermined value;
- means for processing a signal output from the automatic gain controllable amplifier and acquiring predetermined digitalized electric information;
- and
- first, second, and third variable negative capacitors respectively connected to the anode terminal of the photodetector, an output terminal of the preamplifier, and an output terminal of the automatic gain controllable amplifier, wherein:
- the first variable negative capacitor generates a negative capacitance at the input terminal of the preamplifier, the quantity of the negative capacitance is variable according to a control voltage, and each of the first, second, and third variable negative capacitors can be independently controlled through the magnitude of the control voltage.
An optical receiver, comprising:
- a plurality of photodetectors to each of which an optical modulated signal is input and each of which outputs photoelectric current;
- a plurality of signal processing channels respectively connected to said photodetectors, each signal processing channel including:
- a preamplifier, the input terminal of which is connected to an anode terminal of the respective photodetector, which converts a current signal to a first voltage signal and outputs the first voltage signal;
- a voltage amplifier connected to said preamplifier, that amplifies the first voltage signal output from the preamplifier;
- a comparator connected to said voltage amplifier, that compares a second voltage signal output from the voltage amplifier with a reference potential provided in the comparator and outputs a third voltage signal;
- and
- a variable negative capacitor connected to the anode terminal of each photodetector, wherein:
- the variable negative capacitor generates negative capacitance at the input terminal of the preamplifier and the quantity of the negative capacitance is variable according to a control voltage.
Dependencies are inferred from the claim text.