Method and system for accurate gain adjustment of a transimpedance amplifier using a dual replica and servo loop

1. A method for communication, the method comprising:

in a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, a third TIA, and a fourth TIA, each comprising a configurable feedback impedance, and a control loop, the control loop comprising a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs:

configuring a gain level of the first TIA by configuring its feedback impedance;

configuring a gain level of the third TIA by configuring a reference current applied to an input of the first TIA; and

amplifying a received electrical signal to generate an output voltage utilizing the third TIA; and

coupling the output voltage to a first input of a second gain stage wherein a second input of the second gain stage is coupled to an output of said fourth TIA.

2. The method according to claim 1 , wherein the reference current generates a reference voltage at one of the inputs of the gain stage.

3. The method according to claim 2 , wherein the reference voltage controls the output of the gain stage that is coupled to the configurable feedback impedance of the third TIA.

4. The method according to claim 1 , wherein the configurable impedance of the first TIA comprises a configurable array of resistors.

5. The method according to claim 1 , wherein the configurable impedances of the second and third TIAs each comprise a fixed resistor and a voltage-controlled resistance.

6. The method according to claim 5 , comprising configuring the configurable impedances of the second and third TIAs by configuring a gate voltage of a transistor of the voltage-controlled resistance utilizing the output of the gain stage.

7. The method according to claim 1 , comprising generating a differential signal utilizing the output voltage and an output of the fourth TIA.

8. The method according to claim 1 , comprising configuring the output of the second gain stage by configuring an input current of the third TIA.

9. The method according to claim 1 , comprising receiving the electrical signal from a photodetector.

10. A system for communication, the system comprising:

a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, a third TIA, and a fourth TIA, each comprising a configurable feedback impedance, and a control loop, the control loop comprising a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs, the TIA circuit being operable to:

configure a gain level of the first TIA by configuring its feedback impedance;

configure a gain level of the third TIA by configuring a reference current applied to an input of the first TIA;

amplify a received electrical signal to generate an output voltage utilizing the third TIA; and

couple the output voltage to a first input of a second gain stage wherein a second input of the second gain stage is coupled to an output of said fourth TIA.

11. The system according to claim 10 , wherein the reference current generates a reference voltage at one of the inputs of the gain stage.

12. The system according to claim 11 , wherein the reference voltage controls the output of the gain stage that is coupled to the configurable feedback impedance of the third TIA.

13. The system according to claim 10 , wherein the configurable impedance of the first TIA comprises a configurable array of resistors.

14. The system according to claim 10 , wherein the configurable impedances of the second and third TIAs each comprise a fixed resistor and a voltage-controlled resistance.

15. The system according to claim 14 , wherein the TIA circuit is operable to configure the configurable impedances of the second and third TIAs by configuring a gate voltage of a transistor of the voltage-controlled resistance utilizing the output of the gain stage.

16. The system according to claim 10 , wherein the TIA circuit is operable to generate a differential signal utilizing the output voltage and an output of the fourth TIA.

17. The system according to claim 10 , wherein the TIA circuit is operable to configure the output of the second gain stage by configuring an input current of the third TIA.

18. A system for communication, the system comprising:

a transimpedance amplifier (TIA) circuit, the TIA circuit comprising:

a first TIA comprising a first configurable impedance and an output coupled to a first input of a first gain stage;

a second TIA comprising a second configurable impedance and an output coupled to a second input to the first gain stage;

a third TIA comprising a third configurable feedback impedance, an input for receiving an input electrical current, and an output that generates an output voltage of the TIA circuit;

a second gain stage with a first input that receives the output voltage, wherein a second input of the second gain stage is coupled to an output of a fourth TIA; and

a control loop for controlling the gain of the third TIA, the control loop comprising the first gain stage with its output coupled to the second and third configurable impedances.