Transimpedance amplifier circuit
First Claim
1. A transimpedance amplifier circuit comprising:
- an amplifier that amplifies a received signal;
an automatic gain control circuit that controls an amplification gain of the amplifier by a first time constant in accordance with a level of the received signal; and
a first selection circuit that selects the first time constant from a plurality of predetermined values,wherein the first selection circuit includes;
a plurality of resistive elements or a plurality of capacitive elements included in the automatic gain control circuit; and
a first switch element connected in series or parallel with at least some of the plurality of resistive elements or the plurality of capacitive elements and turned on or off based on the control signal to change one of the resistance value of the resistive element and the capacitance value of the capacitive element which decide the value of the first time constant.
1 Assignment
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Accused Products
Abstract
A transimpedance amplifier circuit (1) includes an amplifier (22) that amplifies a received signal, an automatic gain control (AGC) circuit (2) that controls the amplification gain of the amplifier by a first time constant in accordance with the level of the received signal, and a first selection circuit (25) that selects the first time constant from a plurality of predetermined values. This can simultaneously implement a short time constant of an AGC function necessary to instantaneously respond to a burst signal and a long time constant of the AGC function necessary to obtain a satisfactory bit error rate (BER) characteristic in a continuous signal by an inexpensive and compact circuit arrangement.
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Citations
12 Claims
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1. A transimpedance amplifier circuit comprising:
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an amplifier that amplifies a received signal; an automatic gain control circuit that controls an amplification gain of the amplifier by a first time constant in accordance with a level of the received signal; and a first selection circuit that selects the first time constant from a plurality of predetermined values, wherein the first selection circuit includes; a plurality of resistive elements or a plurality of capacitive elements included in the automatic gain control circuit; and a first switch element connected in series or parallel with at least some of the plurality of resistive elements or the plurality of capacitive elements and turned on or off based on the control signal to change one of the resistance value of the resistive element and the capacitance value of the capacitive element which decide the value of the first time constant. - View Dependent Claims (2, 3)
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4. A transimpedance amplifier circuit comprising:
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an amplifier that amplifies a received signal; an automatic gain control circuit that controls an amplification gain of the amplifier by a first time constant in accordance with a level of the received signal; and a first selection circuit that selects the first time constant from a plurality of predetermined values, further comprising; a received signal detection circuit that detects the received signal and outputs a first control signal when a continuous reception time of the received signal exceeds a predetermined time, wherein the first selection circuit selects, based on the first control signal, a longer time constant for the first time constant from at least two predetermined-values. - View Dependent Claims (5)
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6. A transimpedance amplifier circuit comprising:
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an amplifier that amplifies a received signal; an automatic gain control circuit that controls an amplification gain of the amplifier by a first time constant in accordance with a level of the received signal; and a first selection circuit that selects the first time constant from a plurality of predetermined values, further comprising; an automatic offset control circuit that outputs a differential signal based on an output of the amplifier and controls an offset amount of the differential signal by a second time constant; and a second selection circuit that selects the second time constant from a plurality of predetermined values. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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Specification