Configurable laser monitor photodiode in optical modulation amplitude controller
A photodiode current comparison circuit has a first current source coupled to a circuit node configurable to operate in a first mode, a second current source coupled to the circuit node configurable to operate in a second mode opposite the first mode, and a third current source switchable to route a current to the circuit node in response to a data signal using a transistor coupled between the circuit node and the third current source. A photodiode is coupled to the circuit node. In a first configuration, an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal. In a second configuration, a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal. An amplifier provides an error signal of the photodiode.
1. A photodiode current comparison circuit, comprising:
a first current source coupled to a circuit node and configurable to operate in a first mode;
a second current source coupled to the circuit node and configurable to operate in a second mode opposite the first mode;
a third current source switchable to route a current to the circuit node in response to a data signal;
a cross-over circuit comprising inputs coupled for receiving the data signal and outputs for switching polarity of the data signal; and
a photodiode coupled to the circuit node.
2. The photodiode current comparison circuit of claim 1 , wherein an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal.
3. The photodiode current comparison circuit of claim 1 , wherein a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal.
4. The photodiode current comparison circuit of claim 1 , further including an amplifier including a first input coupled to the circuit node, a second input coupled for receiving a reference signal, and an output providing an error signal of the photodiode.
5. A photodiode current comparison circuit, comprising:
a first current source coupled to a circuit node and configurable to operate in a first mode;
a second current source coupled to the circuit node and configurable to operate in a second mode opposite the first mode;
a third current source switchable to route a current to the circuit node in response to a data signal and a complementary data signal;
a first transistor including a first conduction terminal coupled to the circuit node, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the data signal;
a second transistor including a first conduction terminal coupled to a first power supply terminal, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the complementary data signal; and
a photodiode coupled to the circuit node.
6. The photodiode current comparison circuit of claim 5 , wherein an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to the first power supply terminal.
7. The photodiode current comparison circuit of claim 5 , wherein a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a second power supply terminal.
8. The photodiode current comparison circuit of claim 5 , further including an amplifier including a first input coupled to the circuit node, a second input coupled for receiving a reference signal, and an output providing an error signal of the photodiode.
9. A photodiode current comparison circuit in a semiconductor package, comprising:
a first current source coupled to a circuit node;
a second current source coupled to the circuit node;
a control circuit for enabling the first current source or second current source;
a third current source switchable to route a current to the circuit node in response to a data signal;
a cross-over circuit comprising inputs coupled for receiving the data signal and outputs for switching polarity of the data signal; and
a photodiode coupled to the circuit node.
10. The photodiode current comparison circuit of claim 9 , wherein an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal.
11. The photodiode current comparison circuit of claim 9 , wherein a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal.
12. The photodiode current comparison circuit of claim 9 , further including an amplifier including a first input coupled to the circuit node, a second input coupled for receiving a reference signal, and an output providing an error signal of the photodiode.
13. The photodiode current comparison circuit of claim 9 , wherein the first current source is referenced to a first power supply potential and the second current source is referenced to a second power supply potential.
14. A photodiode current comparison circuit in a semiconductor package, comprising:
a first current source coupled to a circuit node;
a second current source coupled to the circuit node;
a control circuit for enabling the first current source or second current source;
a third current source switchable to route a current to the circuit node in response to a data signal;
a first transistor including a first conduction terminal coupled to the circuit node, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the data signal;
a second transistor including a first conduction terminal coupled to a first power supply terminal, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the data signal; and
a photodiode coupled to the circuit node.
15. The photodiode current comparison circuit of claim 14 , wherein an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to the first power supply terminal.
16. The photodiode current comparison circuit of claim 14 , wherein a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a second power supply terminal.
17. The photodiode current comparison circuit of claim 14 , further including an amplifier including a first input coupled to the circuit node, a second input coupled for receiving a reference signal, and an output providing an error signal of the photodiode.
18. The photodiode current comparison circuit of claim 14 , wherein the first current source is referenced to a first power supply potential and the second current source is referenced to a second power supply potential.
19. A method of making a photodiode current comparison circuit, comprising:
providing a first current source coupled to a circuit node;
providing a second current source coupled to the circuit node;
providing a control circuit for enabling the first current source or second current source;
providing a third current source switchable to route a current to the circuit node in response to a data signal;
providing a first transistor including a first conduction terminal coupled to the circuit node, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the data signal;
providing a second transistor including a first conduction terminal coupled to a first power supply terminal, a second conduction terminal coupled to the third current source, and a control terminal coupled for receiving the data signal; and
providing a photodiode coupled to the circuit node.
20. The method of claim 19 , wherein an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to the first power supply terminal.
21. The method of claim 19 , wherein a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a second power supply terminal.
22. The method of claim 19 , further including providing an amplifier including a first input coupled to the circuit node, a second input coupled for receiving a reference signal, and an output providing an error signal of the photodiode.
23. The method of claim 19 , further including providing a cross-over circuit comprising inputs coupled for receiving the data signal and outputs for switching polarity of the data signal.
24. The method of claim 19 , wherein the first current source is referenced to a first power supply potential and the second current source is referenced to a second power supply potential.