Method and system for continuous gain control in a feedback transimpedance amplifier

1. A method for optical communication, the method comprising:

in a transimpedance amplifier (TIA) comprising a gain stage, a feedback resistance for said gain stage, a current sense resistor, and a feedback current control circuit:

receiving an input current at an input of said gain stage;

directing a current through said current sense resistor to said feedback current control circuit; and

generating an output voltage proportional to said input current and a gain of said TIA, wherein said gain is configured by providing, by said feedback current control circuit, a current to said input of said gain stage that is a proportion (α) of said current directed through said current sense resistor.

2. The method according to claim 1 , comprising configuring said proportion α of said current provided by said feedback current control circuit to said input of said gain stage by applying a differential voltage to control terminals of a transistor pair in said feedback current control circuit.

3. The method according to claim 1 , comprising configuring said proportion α of said current provided by said feedback current control circuit to said input of said gain stage by configuring a voltage coupled to one of a pair of transistors in said feedback current control circuit.

4. The method according to claim 1 , comprising configuring a gain of said gain stage by applying a differential voltage to control terminals of a transistor pair in said gain stage.

5. The method according to claim 1 , comprising configuring a gain of said gain stage to equal A/(1+α), where A is the maximum gain of said gain stage.

6. The method according to claim 1 , comprising receiving said input current from a photodetector.

7. The method according to claim 1 , wherein said TIA comprises bipolar transistors.

8. The method according to claim 7 , wherein said gain stage and said feedback current control circuit each comprise an emitter-coupled transistor pair.

9. The method according to claim 1 , wherein said TIA comprises metal-oxide semiconductor (CMOS) transistors.

10. The method according to claim 1 , wherein said feedback resistor and said current sense resistor comprise fixed resistors.

11. A system for optical communication, the system comprising:

a transimpedance amplifier (TIA) comprising a gain stage, a feedback resistance for said gain stage, a current sense resistor, and a feedback current control circuit, said TIA being operable to:

receive an input current at an input of said gain stage;

direct a current through said current sense resistor to said feedback current control circuit; and

generate an output voltage proportional to said input current and a gain of said TIA, wherein said gain is configured by providing, by said feedback current control circuit, a current to said input of said gain stage that is a proportion (α) of said current directed through said feedback current sense resistor.

12. The system according to claim 11 , wherein said TIA is operable to configure said proportion α of said current provided by said feedback current control circuit to said input of said gain stage by applying a differential voltage to control terminals of a transistor pair in said feedback current control circuit.

13. The system according to claim 12 , wherein said TIA is operable to configure said proportion α of said current provided by said feedback current control circuit to said input of said gain stage by configuring a voltage coupled to one of a pair of transistors in said feedback current control circuit.

14. The system according to claim 11 , wherein said TIA is operable to configure a gain of said gain stage by applying a differential voltage to control terminals of a transistor pair in said gain stage.

15. The system according to claim 11 , wherein said TIA is operable to configure a gain of said gain stage to equal A/(1+α), where A is the maximum gain of said gain stage.

16. The system according to claim 11 , wherein said TIA is operable to receive said input current from a photodetector.

17. The system according to claim 11 , wherein said TIA comprises bipolar transistors.

18. The system according to claim 17 , wherein said gain stage and said feedback current control circuit each comprise an emitter-coupled transistor pair.

19. The system according to claim 11 , wherein said TIA comprises metal-oxide semiconductor (CMOS) transistors.

20. A system for optical communication, the system comprising:

a transimpedance amplifier (TIA) comprising a gain stage, a feedback resistance for said gain stage, a current sense resistor, and a feedback current control circuit, said TIA being operable to:

receive an input current at an input of said gain stage;

direct a current through said current sense resistor to said feedback current control circuit; and

generate an output voltage proportional to said input current and a gain of said TIA, wherein said gain is configured by providing, by said feedback current control circuit, a proportion (α) of said current directed through said current sense resistor to said input of said gain stage, and wherein said gain is equal to R F /(1=α*R F /R FX ) where R F is a resistance of said feedback resistance and R FX is a resistance of said current sense resistor.