Multiplexed integrating amplifier for loss of signal detection
View Patent ↗A loss of signal circuit has a multiplexer and a photodiode coupled to a first input of the multiplexer. A reference signal generator is coupled to a second input of the multiplexer. An amplifier is coupled to an output of the multiplexer. A demultiplexer includes an input of the demultiplexer coupled to an output of the amplifier. A first capacitor is coupled to a first output of the demultiplexer. A second capacitor is coupled to a second output of the demultiplexer. A comparator has a first input coupled to the first output of the demultiplexer and a second input of the comparator is coupled to the second output of the demultiplexer.
1. A semiconductor device, comprising:
a multiplexer;
a photodiode coupled to a first input of the multiplexer;
a reference signal generator coupled to a second input of the multiplexer;
an amplifier coupled to an output of the multiplexer; and
a demultiplexer including an input of the demultiplexer coupled to an output of the amplifier.
2. The semiconductor device of claim 1 , further including:
a first capacitor coupled to a first output of the demultiplexer; and
a second capacitor coupled to a second output of the demultiplexer.
3. The semiconductor device of claim 2 , further including a comparator comprising a first input of the comparator coupled to the first output of the demultiplexer and a second input of the comparator coupled to the second output of the demultiplexer.
4. The semiconductor device of claim 3 , further including an output of the comparator coupled to an input of the reference signal generator.
5. The semiconductor device of claim 1 , further including a limiting amplifier coupled to the photodiode in parallel with the multiplexer.
6. The semiconductor device of claim 1 , further including a transconductance amplifier coupled from an output of the amplifier to an input of the amplifier.
7. A semiconductor device, comprising:
a multiplexer;
a data input coupled to a first input of the multiplexer;
a reference signal generator coupled to a second input of the multiplexer; and
an amplifier coupled to an output of the multiplexer.
8. The semiconductor device of claim 7 , wherein the amplifier includes a plurality of stages.
9. The semiconductor device of claim 8 , further including:
a first rectifier coupled to an output of a first stage of the amplifier; and
a second rectifier coupled to an output of a second stage of the amplifier.
10. The semiconductor device of claim 7 , further including a rectifier coupled to an output of the amplifier.
11. The semiconductor device of claim 10 , further including a demultiplexer coupled to an output of the rectifier.
12. The semiconductor device of claim 11 , further including:
a first capacitor coupled to a first output of the demultiplexer; and
a second capacitor coupled to a second output of the demultiplexer.
13. The semiconductor device of claim 12 , further including a comparator coupled to the first capacitor and second capacitor.
14. A method of detecting signal loss, comprising:
receiving a data signal at a first input of a multiplexer;
receiving a reference signal at a second input of the multiplexer;
outputting the reference signal from the multiplexer to an amplifier during a first time period;
coupling an output of the amplifier to a first capacitor during the first time period;
outputting the data signal from the multiplexer to the amplifier during a second time period; and
coupling the output of the amplifier to a second capacitor during the second time period.
15. The method of claim 14 , further including outputting a 0 mV signal from the multiplexer for a third time period.
16. The method of claim 15 , further including modifying a bias of the amplifier during the third time period.
17. The method of claim 14 , further including comparing a voltage potential of the first capacitor to a voltage potential of the second capacitor.
18. The method of claim 17 , further including increasing a magnitude of the reference signal when the voltage potential of the second capacitor falls below the voltage potential of the first capacitor.
19. The method of claim 14 , further including disabling a second stage of the amplifier while a first stage of the amplifier remains coupled to the first capacitor or second capacitor.
20. A method of detecting signal loss, comprising:
receiving a data signal at a first input of a multiplexer;
receiving a reference signal at a second input of the multiplexer;
outputting the reference signal from the multiplexer to an amplifier during a first time period; and
outputting the data signal from the multiplexer during a second time period.
21. The method of claim 20 , further including zeroing the amplifier during a third time period.
22. The method of claim 20 , further including rectifying an output of the amplifier to create a direct current (DC) signal.
23. The method of claim 22 , further including:
coupling the DC signal to a first capacitor during the first time period; and
coupling the DC signal to a second capacitor during the second time period.
24. The method of claim 23 , further including comparing a voltage potential of the first capacitor to a voltage potential of the second capacitor.
25. The method of claim 20 , further including adjusting the reference signal based on a detected temperature.