Claims
- 1. A three stage operational amplifier for controlling bias current in a laser diode comprising:
a first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; a second stage including a capacitor, said second stage configured to integrate an output current produced by the first stage to generate a first output voltage; and a third stage including an output buffer, said third stage configured to receive as input the first output voltage to generate a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode; wherein the differential amplifier comprises a symmetrical assembly of transistors such that a transconductance of said differential amplifier approaches a constant when a difference between the desired magnitude of the laser diode voltage and the laser diode voltage is substantially zero volts, said transconductance of said differential amplifier increasing exponentially as the difference increases.
- 2. The three stage operational amplifier of claim 1, wherein
the differential amplifier comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor; a base of the first transistor is connected to the laser diode voltage, a collector of the first transistor transmits a first current to a current mirror, and the emitter of the first transistor is connected to a base of the second transistor, a first current source, and an emitter of the third transistor; a collector of the second transistor is connected to a power supply voltage and an emitter of the second transistor is connected to a base of the fourth transistor and a second current source; a collector of the third transistor is connected to ground and a base of said third transistor is connected to a third current source and an emitter of the fifth transistor; a collector of the fourth transistor is connected to the ground and an emitter of the fourth transistor is connected to a fourth current source, a base of the fifth transistor, and an emitter of the sixth transistor; a collector of the fifth transistor is connected to the power supply voltage; a base of the sixth transistor is connected to the reference voltage and a collector of the sixth transistor transmits a second current to the current mirror; and the current mirror is configured to produce the output current based on a difference between the first current and the second current.
- 3. The three stage operational amplifier of claim 1, wherein
the second output voltage of the third stage is connected to and regulates a voltage controlled current source, said voltage controlled current source supplying the bias current as determined by the second output voltage.
- 4. The three stage operational amplifier of claim 1, wherein
the reference voltage is set to the desired magnitude of the laser diode voltage.
- 5. A three stage operational amplifier for controlling bias current in a laser diode comprising:
a first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; a second stage including a capacitor, said second stage configured to integrate an output current produced by the first stage to produce a first output voltage; a third stage including an output buffer, said third stage configured to receive as input the first output voltage to produce a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode; and a voltage comparator to compare the laser diode voltage to the reference voltage, said voltage comparator directing boosting current from a current source to the second stage when a difference between said laser diode voltage and said reference voltage is one of greater than and equal to a predefined amount.
- 6. The three stage operational amplifier of claim 5, wherein
the laser diode is not in a linear operating range when the difference is in excess of the predefined amount.
- 7. The three stage operational amplifier of claim 5, further comprising
a charge switch; the charge switch being configured to transmit the boosting current to ground when the voltage comparator indicates that the difference between the laser diode voltage and the reference voltage is less than the predefined amount; and the charge switch being configured to transmit the boosting current to the second stage when the voltage comparator indicates that the difference between the laser diode voltage and the reference voltage is one of greater than and equal to the predefined amount.
- 8. The three stage operational amplifier of claim 7, wherein
the charge switch comprises a first transistor and a second transistor; a gate of the first transistor being connected to a voltage output of the voltage comparator, a drain of the first transistor connected to the second stage, a source of the first transistor connected to the current source and to a source of the second transistor; a gate of the second transistor connected to a bias voltage and a drain of the second transistor connected to the ground; the bias voltage set such that when the voltage output of the voltage comparator indicates that the difference between the laser diode voltage and the reference voltage is one of greater than and equal to the predefined amount substantially all of the boosting current flows from the current source through the first transistor to the second stage; and the bias voltage set such that when the voltage output of the voltage comparator indicates that the difference between the laser diode voltage and the reference voltage is less than the predefined amount substantially all of the boosting current flows from the current source through the second transistor to the ground.
- 9. The three stage operational amplifier of claim 5, wherein
the reference voltage is set to the desired magnitude of the laser diode voltage.
- 10. A three stage operational amplifier for controlling bias current in a laser diode comprising:
a first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; a plurality of second stages, each of said plurality of second stages including a capacitor, one of said plurality of second stages producing a first output voltage from an output current produced by the first stage; a third stage including an output buffer, said third stage configured to receive as input the first output voltage to produce a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode; and a voltage comparator to determine a difference between the laser diode voltage and the reference voltage, said voltage comparator controlling selection of the one of said plurality of second stages by reference to said difference between said laser diode voltage and said reference voltage.
- 11. The three stage operational amplifier of claim 10, wherein the plurality of second stages include
a slow second stage including a first capacitor; a fast second stage including a second capacitor and a resistor in series, said fast second stage providing comparatively greater gain than the slow second stage across a range of high frequencies.
- 12. The three stage operational amplifier of claim 11, wherein
the voltage comparator is configured to select the fast second stage from the plurality of second stages when the difference exceeds a predefined amount; and the voltage comparator is configured to select the slow second stage from the plurality of second stages when the difference is one of less than and equal to the predefined amount.
- 13. The three stage operational amplifier of claim 12, wherein
the laser diode is not in a linear operating range when the difference in excess of the predefined amount.
- 14. The three stage operational amplifier of claim 12, further comprising
a first switch, a second switch, a third switch, and a second output buffer; an output of the voltage comparator being inverted and connected as a control signal to the first switch, an output section of a first of the plurality of second stages connected to said first switch as a current source, and a ground connected to said first switch as current drain for said first switch; the output of the voltage comparator being inverted and connected as a control signal to the second switch, an output of the second output buffer connected to said second switch as a current source for said second switch, an input section of a second of the plurality of second stages connected to said second switch as a current drain for said second switch; and the output of the voltage comparator being connected as a control signal to the third switch, said third switch connecting the first of the plurality of second stages to the output buffer; whereby, when the output of the voltage comparator is set to a first level, the first of the plurality of second stages is said one of said plurality of second stages producing a first output voltage from an output current produced by the first stage and when the output of the voltage comparator is set to a second level, the second of the plurality of second stages is said one of said plurality of second stages producing a first output voltage from an output current produced by the first stage.
- 15. The three stage operational amplifier of claim 10, wherein
the reference voltage is set to the desired magnitude of the laser diode voltage.
- 16. A passive optical network with increased data bandwidth comprising:
a plurality of optoelectronic transceivers, a coordinator, a controller, an optical combiner, and a shared communication line; the coordinator configured to assign each of the plurality of optoelectronic transceivers to a separate portion of a cyclical time period; the controller configured to turn optical data transmit capabilities of the plurality of optoelectronic transceivers on and off during their respective separate portions of the cyclical time period; the optical combiner configured to relay optical data received from the plurality of optoelectronic transceivers to the shared communication line; each of the plurality of optoelectronic transceivers including an operational amplifier with a first stage, a second stage, and a third stage, said operational amplifier controlling bias current in a laser diode; the first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; the second stage including a capacitor, said second stage configured to integrate an output current produced by the first stage to generate a first output voltage; and the third stage including an output buffer, said third stage configured to receive as input the first output voltage to generate a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode, wherein the differential amplifier comprises a symmetrical assembly of transistors such that a transconductance of said differential amplifier approaches a constant when a difference between the desired magnitude of the laser diode voltage and said laser diode voltage is substantially zero volts, said transconductance of said differential amplifier increasing exponentially as the difference increases.
- 17. A passive optical network with increased data bandwidth comprising:
a plurality of optoelectronic transceivers, a coordinator, a controller, an optical combiner, and a shared communication line; the coordinator configured to assign each of the plurality of optoelectronic transceivers to a separate portion of a cyclical time period; the controller configured to turn optical data transmit capabilities of the plurality of optoelectronic transceivers on and off during their respective separate portions of the cyclical time period; the optical combiner configured to relay optical data received from the plurality of optoelectronic transceivers to the shared communication line; each of the plurality of optoelectronic transceivers including an operational amplifier with a first stage, a second stage, a third stage, and a voltage comparator, said operational amplifier controlling bias current in a laser diode; the first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; the second stage including a capacitor, said second stage configured to integrate an output current produced by the first stage to produce a first output voltage; the third stage including an output buffer, said third stage configured to receive as input the first output voltage to produce a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode; and the voltage comparator configured to compare the laser diode voltage to the reference voltage, said voltage comparator directing boosting current from a current source to the second stage when a difference between said laser diode voltage and said reference voltage is one of greater than and equal to a predefined amount.
- 18. A passive optical network with increased data bandwidth comprising:
a plurality of optoelectronic transceivers, a coordinator, a controller, an optical combiner, and a shared communication line; the coordinator configured to assign each of the plurality of optoelectronic transceivers to a separate portion of a cyclical time period; the controller configured to turn optical data transmit capabilities of the plurality of optoelectronic transceivers on and off during their respective separate portions of the cyclical time period; the optical combiner configured to relay optical data received from the plurality of optoelectronic transceivers to the shared communication line; each of the plurality of optoelectronic transceivers including an operational amplifier with a first stage, a second stage, a third stage, and a voltage comparator, said operational amplifier controlling bias current in a laser diode; the first stage including a differential amplifier, said first stage configured to receive as input a reference voltage and a laser diode voltage, said laser diode voltage representing an optical output strength of a laser diode, said reference voltage corresponding to a desired magnitude of said laser diode voltage; the plurality of second stages, each of said plurality of second stages including a capacitor, one of said plurality of second stages producing a first output voltage from an output current produced by the first stage; the third stage including an output buffer, said third stage configured to receive as input the first output voltage to produce a second output voltage approximately equal to said first output voltage, said second output voltage controlling a bias current for the laser diode; and the voltage comparator configured to determine a relationship between the laser diode voltage and the reference voltage, said voltage comparator controlling selection of the one of said plurality of second stages by reference to said relationship between said laser diode voltage and said reference voltage.
Parent Case Info
[0001] The present application claims priority, under 35 U.S.C. 120, to a United States Non-Provisional Patent Application, which is incorporated herein by reference, entitled “SYSTEM FOR CONTROLLING BIAS CURRENT IN LASER DIODES WITH IMPROVED SWITCHING RATES,” filed on Jul. 2, 2002, and identified by attorney reference number 9775-085-999 and application Ser. No. 10/188,575.
[0002] The present application also claims priority, under 35 U.S.C. 119(e), to a United States Provisional Patent Application, which is incorporated herein by reference, entitled “SYSTEM FOR CONTROLLING BIAS CURRENT IN LASER DIODES WITH IMPROVED SWITCHING RATES,” filed on Sep. 5, 2002, and identified by attorney reference number 9775-130-888 and serial No. 60/408,587.
Provisional Applications (1)
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Number |
Date |
Country |
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60408587 |
Sep 2002 |
US |