Optical receiver preamplifier dynamic range enhancing circuit and method
First Claim
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1. In an optical receiver, a preamplifier circuit responsive to a signal from an electro-optical detector coupling to an input of the preamplifier, the signal having a DC portion and an AC portion, comprising:
- a variable DC shunt path coupling to the input of the preamplifier, the amount of current shunted being proportional to the DC portion of the signal from the detector; and
,a variable impedance AC shunt path, separate from the DC shunt path, coupling to the input of the preamplifier, the impedance being proportional to the DC portion of the signal from the detector.
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Abstract
A preamplifier overload control circuit which enhances the dynamic range of the preamplifier. Separate paths shunt corresponding DC and AC components of the signal from an electro-optical device away from the preamplifier input. The amount of shunting in both paths are controlled by a common control signal, here the average DC value of the signal, such that substantially all of the DC signal is shunted away from the preamplifier input.
44 Citations
16 Claims
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1. In an optical receiver, a preamplifier circuit responsive to a signal from an electro-optical detector coupling to an input of the preamplifier, the signal having a DC portion and an AC portion, comprising:
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a variable DC shunt path coupling to the input of the preamplifier, the amount of current shunted being proportional to the DC portion of the signal from the detector; and
,a variable impedance AC shunt path, separate from the DC shunt path, coupling to the input of the preamplifier, the impedance being proportional to the DC portion of the signal from the detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of enhancing the dynamic range of an optical receiver preamplifier in an optical system, the receiver having an electro-optical detector coupling to the input of the preamplifier, the preamplifier amplifying a signal from the detector, the signal having a DC portion, and an AC portion, comprising the steps of:
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shunting along a first path a DC current away from the input of the preamplifier, using an FET biased in saturation to provide the shunting; and
,shunting along a second path an AC signal away from the input of the preamplifier, the shunted signal being in proportion to the DC portion of the signal from the detector. - View Dependent Claims (13, 14, 15, 16)
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Specification