Trans-impedance amplifier with replica gain control
View Patent ↗This disclosure relates to the field of amplifiers for multi-level optical communication and more particularly to techniques for trans-impedance amplifiers (TIA) with gain control. The claimed embodiments address the problem of implementing a low cost TIA that exhibits high linearity, low noise, low power, and wide bandwidth. More specifically, some claims are directed to approaches for providing TIA gain control using a plurality of inverter-based replica gain control cells controlled by a feedback loop to manage the current into the amplifying output stage and thereby the TIA output voltage.
1. A trans-impedance amplifier for amplifying an input signal, the trans-impedance amplifier comprising:
a first common node to receive a first current input of the input signal;
a first inverting amplifier having a first amplifier input coupled to the first common node, and having a first voltage output;
a first replica gain control module comprising a first module input coupled to the first common node, and at least one replica gain control cell coupled to the first module input,
wherein the first replica gain control module diverts a first portion of the first current input away from the first inverting amplifier to effect the first voltage output;
a second common node to receive a second current input of the input signal; and
a second replica gain control module having a second module input coupled to the second common node to receive a second portion of the second current input.
2. The trans-impedance amplifier of claim 1 , wherein at least one replica gain control cell further comprises at least one control input to control a magnitude of the first portion of the first current input.
3. The trans-impedance amplifier of claim 2 , wherein at least one replica gain control cell further comprises at least one pass gate device coupled to the first module input and coupled to at least one control input.
4. The trans-impedance amplifier of claim 2 , further comprising a gain control loop coupled to the first voltage output and at least one control input.
5. The trans-impedance amplifier of claim 4 , wherein the gain control loop provides a discrete control signal coupled to at least one control input.
6. The trans-impedance amplifier of claim 4 , wherein the gain control loop provides a linear control signal coupled to at least one control input.
7. The trans-impedance amplifier of claim 4 , wherein the gain control loop uses analog or digital circuits to change a number of replica gain control cells enabled.
8. The trans-impedance amplifier of claim 4 , further comprising analog or digital circuits to control tuning voltages to change at least one replica gain control impedance.
9. The trans-impedance amplifier of claim 1 , further comprising:
a second inverting amplifier having a second amplifier input coupled to the second common node, and having a second voltage output
wherein the second replica gain control module diverts the second portion of the second current input away from the second inverting amplifier to effect the second voltage output, and wherein a voltage difference between the first voltage output and the second voltage output comprise a differential voltage output.
10. The trans-impedance amplifier of claim 9 , wherein the second replica gain control module further comprises at least one control input to control a magnitude of the second portion of the second current input.
11. The trans-impedance amplifier of claim 9 , wherein the second replica gain control module further comprises at least one pass gate device.
12. The trans-impedance amplifier of claim 9 , further comprising a gain control loop coupled to the first voltage output and at least one control input.
13. The trans-impedance amplifier of claim 12 , wherein the gain control loop provides a discrete control signal.
14. The trans-impedance amplifier of claim 12 , wherein the gain control loop provides a linear control signal coupled to at least one control input.
15. A system for amplifying an input signal, the system comprising:
a first common node to receive a first current input of the input signal;
a first inverting amplifier having a first amplifier input coupled to the first common node, and having a first voltage output;
a first replica gain control module comprising a first module input coupled to the first common node, and at least one replica gain control cell coupled to the first module input,
wherein the first replica gain control module diverts a first portion of the first current input away from the first inverting amplifier to effect the first voltage output;
a second common node to receive a second current input of the input signal;
a second replica gain control module having a second module input coupled to the second common node to receive a second portion of the second current input; and
a gain control loop to control a magnitude of at least one of, the first portion of the first current input, or the second portion of the second current input.
16. The system of claim 15 , further comprising an analog control loop having a first analog voltage tuning signal.
17. The system of claim 16 , wherein the first analog tuning voltage signal changes an impedance of at least one replica gain control module.
18. The system of claim 16 , wherein the first analog voltage tuning signal derives from a digital-to-analog converter (DAC).
19. The system of claim 15 , further comprising an analog control loop having a second analog voltage tuning signal.
20. The system of claim 15 , further comprising:
a second inverting amplifier having a second amplifier input coupled to the second common node and having a second voltage output,
wherein the second replica gain control module diverts a second portion of the second current input away from the second inverting amplifier to effect the second voltage output, and wherein a voltage difference between the first voltage output and the second voltage output comprise a differential voltage output.