Very high speed optical receiver with a cascadable differential action feedback driver
AssigneeBell Communications Research, Inc.
InventorsGee-Kung Chang, Ting P. Liu
Life of this patent
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Abstract
Our invention is a differential transimpedance amplifier circuit with shunt-shunt local feedback gain stages. These shunt-shunt feedback gain stages comprise an additional resistor and two transistors in a shunt-shunt feedback configuration to provide a low output impedance while maintaining the transimpedance gain. Cascading circuits of this structure results in a high bandwidth receiver with sufficient gain to drive conventional data regeneration circuits.
Claims11
A high speed optical receiver circuit including a differential amplifier circuit, said differential amplifier circuit having a structure comprising a first and second current path connected between two DC biasing sources, each of said current paths including an input transistor, a load resistor, and a second transistor connected in series, each of said input and second transistors having an emitter, a base, and a collector, said circuit comprising:
- a photodiode connected between said emitters of said input transistor with the bases of said input transistors biased at different levels,
- a pair of shunt-shunt feedback gain circuits each comprising a second resistor and a third transistor connected in series and each associated with one of said current paths, each of said third transistors having an emitter, a base, and a collector, the base of each of said second transistors being connected to said second resistor and the collector of said third transistor of the associated shunt-shunt feedback gain stage, and the base of each third transistor being connected to said load resistor and the collector of said input transistor of the associated one of said current paths;
- and
- an output node connected to said base of at least one of said second transistors.
A high speed optical receiver comprising:
- a differential transimpedance amplifier having two input transistors with the bases of the input transistors biased at different levels;
- a photodiode biased between the emitters of the two input transistors;
- shunt-shunt feedback gain means for providing transimpedance gain and providing an output impedance reduced by the value of the open loop gain of said shunt-shunt feedback gain means;
- and
- two output nodes at which complementary voltage outputs are produced responsive to the current induced by said photodiode.
A high speed receiver circuit comprising:
- a differential transimpedance amplifier circuit having a pair of input transistors with the bases of said input transistors biased at different levels;
- a signal detector coupled to and biased between the emitters of said input transistors;
- and
- output impedance means connected to each of said input transistors, said output impedance means comprising a shunt-shunt feedback gain circuit having a feedback stage and output load stage.
Dependencies are inferred from the claim text.