Transimpedance amplifier with variable inductance input reducing peak variation over gain
View Patent ↗A transimpedance amplifier (TIA) structure includes an input node with a variable inductance component serving to reduce variation in peak amplitude over different gain conditions. According to certain embodiments, an inductor at the TIA input has a first node in communication with a Field Effect Transistor (FET) drain, and a second node in communication with the FET source. A control voltage applied to the FET gate effectively controls the input inductance by adding a variable impedance across the inductor. Under low gain conditions, lowering of inductance afforded by the control voltage applied to the FET reduces voltage peaking. TIAs in accordance with embodiments may be particularly suited to operate over a wide dynamic range to amplify incoming electrical signals received from a photodiode.
1. An apparatus comprising:
a variable inductance component located between a photodiode and a transimpedance amplifier, the variable inductance component including an inductor and having,
an input node, and
an output node in electrical communication with the transimpedance amplifier; and
the variable inductance component further comprising a switching device including,
a first contact in electrical communication with the input node,
a second contact in electrical communication with the output node, and
a third contact in electrical communication with a variable control voltage to change an effective inductance at the first node, wherein the variable control voltage is configured to reduce peaking at an output node of the TIA under low gain conditions.
2. An apparatus as in claim 1 wherein:
the switching device comprises a MOSFET;
the first contact comprises a drain of the MOSFET;
the second contact comprises a source of the MOSFET;
the third contact comprises a gate of the MOSFET in communication with a variable voltage source; and
the gate is in communication with a variable voltage source through a resistor.
3. An apparatus as in claim 1 wherein the switching device comprises a comprises a FinFet.
4. An apparatus as in claim 1 wherein the TIA is configured to operate with a dynamic range of about 18 dB to about 20 dB.
5. An apparatus as in claim 1 wherein the TIA is configured to operate with a dynamic range of about 15 dB to about 18 dB.
6. An apparatus as in claim 1 wherein the peaking is reduced by about 3 dB.
7. An apparatus as in claim 1 wherein the input node is in electrical communication with the photodiode across a chip boundary.
8. An apparatus as in claim 1 further comprising another inductor between the photodiode and the input node.
9. An apparatus comprising:
a variable inductance component including an inductor and located between a photodiode and a transimpedance amplifier, the variable inductance component having,
an input node, and
an output node in electrical communication with the transimpedance amplifier; and
the variable inductance component further comprising a switching device including,
a first contact in electrical communication with the input node,
a second contact in electrical communication with the output node, and
a third contact in electrical communication with a variable control voltage to change an effective inductance at the first node, wherein the input node is in electrical communication with the photodiode across a chip boundary.
10. An apparatus as in claim 9 wherein the variable control voltage is configured to reduce peaking at an output node of the TIA under low gain conditions.
11. An apparatus as in claim 10 wherein the peaking is reduced by about 3 dB.
12. An apparatus as in claim 9 wherein:
the switching device comprises a MOSFET;
the first contact comprises a drain of the MOSFET;
the second contact comprises a source of the MOSFET;
the third contact comprises a gate of the MOSFET in communication with a variable voltage source; and
the gate is in communication with a variable voltage source through a resistor.
13. An apparatus as in claim 9 wherein the switching device comprises a FinFet.
14. An apparatus as in claim 9 wherein the TIA is configured to operate with a dynamic range of about 18 dB to about 20 dB.
15. An apparatus as in claim 9 wherein the TIA is configured to operate with a dynamic range of about 15 dB to about 18 dB.
16. An apparatus as in claim 9 further comprising another inductor between the photodiode and the input node.
17. An apparatus comprising:
a variable inductance component located between a photodiode and a transimpedance amplifier, the variable inductance component including an inductor and having,
an input node, and
an output node in electrical communication with the transimpedance amplifier;
the variable inductance component further comprising a switching device including,
a first contact in electrical communication with the input node,
a second contact in electrical communication with the output node, and
a third contact in electrical communication with a variable control voltage to change an effective inductance at the first node; and
another inductor between the photodiode and the first contact.
18. An apparatus as in claim 17 wherein the variable control voltage is configured to reduce peaking at an output node of the TIA under low gain conditions.
19. An apparatus as in claim 18 wherein the peaking is reduced by about 3 dB.
20. An apparatus as in claim 17 wherein:
the switching device comprises a MOSFET;
the first contact comprises a drain of the MOSFET;
the second contact comprises a source of the MOSFET;
the third contact comprises a gate of the MOSFET in communication with a variable voltage source; and
the gate is in communication with a variable voltage source through a resistor.
21. An apparatus as in claim 17 wherein the switching device comprises a FinFet.
22. An apparatus as in claim 17 wherein the TIA is configured to operate with a dynamic range of about 18 dB to about 20 dB.
23. An apparatus as in claim 17 wherein the TIA is configured to operate with a dynamic range of about 15 dB to about 18 dB.
24. An apparatus as in claim 17 wherein the variable control voltage is configured to reduce peaking at an output node of the TIA under low gain conditions.
25. An apparatus as in claim 24 wherein the peaking is reduced by about 3 dB.
26. An apparatus as in claim 17 wherein the input node is in electrical communication with the photodiode across a chip boundary.