Highly linear, low-power, transconductor
View Patent ↗Systems and methods which implement a transconductor replica feedback (TRF) block in a transconductor circuit are shown. In accordance with embodiments, the TRF block comprises a feedback transistor disposed as a replica of a corresponding transconductance transistor of the transconductor circuit. The TRF block provides enhanced looking-in degeneration impedance for the transconductor circuit, thereby allowing for higher linearity and lower power at the same time. TRF transconductors of embodiments can be implemented in, or otherwise applied to, various different circuits such as LNAs, filters, etc.
1. A transconductor circuit comprising:
a transconductance transistor; and
a feedback transistor, wherein the feedback transistor is provided in the transconductor circuit as a replica of the transconductor transistor, wherein the feedback transistor is both disposed as a replica of the transconductance transistor and configured to perform as a replica of the transconductance transistor, and wherein the feedback transistor is operable to sense current change in the transconductance transistor and to control a corresponding current change in another transistor of the transconductor circuit to offset the sensed current change.
2. A transconductor circuit comprising:
a transconductance transistor; and
a feedback transistor, wherein the feedback transistor is provided in the transconductor circuit as a replica of the transconductor transistor, wherein the feedback transistor is both disposed as a replica of the transconductance transistor and configured to perform as a replica of the transconductance transistor, and wherein the feedback transistor is operable to provide an effective de-generating resistance which is higher than that of a degeneration resistor coupled to the transconductance transistor.
3. The transconductor circuit of claim 1 , wherein the another transistor comprises a bias transistor operable to bias the transconductance transistor.
4. The transconductor circuit of claim 1 , wherein the feedback transistor disposed as a replica of the transconductance transistor is disposed to appear to an input node of in the transconductor circuit as a replica of the transconductance transistor.
5. The transconductor circuit of claim 4 , wherein the feedback transistor configured to perform as a replica of the transconductance transistor is configured so that various operating characteristics of the feedback transistor are provided in a reduced performance ratio with respect to corresponding operating characteristics of the transconductance transistor.
6. The transconductor circuit of claim 1 , further comprising:
a transimpedance resistor coupled to the feedback transistor.
7. The transconductor circuit of claim 6 , wherein the transimpedance resistor is operable to increase a loop gain of the transconductor circuit.
8. The transconductor circuit of claim 6 , wherein the transimpedance resistor is operable to reduce current in the feedback transistor.
9. A system comprising:
a transconductor circuit having a transconductor replica feedback block therein, wherein the transconductor replica feedback block is operable to sense current change in a first component of the transconductor circuit and to control a corresponding current change in a second component of the transconductor circuit to offset the sensed current change, wherein a feedback component of the transconductor replica feedback block is provided as a replica of the first component, wherein the first component comprises a transconductance transistor, the second component comprises a bias transistor, and the feedback component comprises a feedback transistor.
10. The system of claim 9 , wherein the feedback component is disposed as a replica of the first component.
11. The system of claim 10 , wherein the feedback component is disposed to appear to an input node of the transconductor circuit as the first component.
12. The system of claim 9 , wherein the feedback component is configured to perform as a replica of first component.
13. The system of claim 12 , wherein the feedback component is configured to have a reduced performance ratio with respect to the first component.
14. The system of claim 9 , further comprising:
a transimpedance resistor coupled to the feedback transistor.
15. The system of claim 14 , wherein the transimpedance resistor is operable to increase a loop gain of the transconductor circuit.
16. The system of claim 14 , wherein the transimpedance resistor is operable to reduce current in the feedback transistor.
17. A method comprising:
providing a transconductor replica feedback block in a transconductor circuit;
sensing changes in current in a transconductance transistor of the transconductor circuit, wherein the transconductor replica feedback block is operable to provide the sensing changes in current in the transconductance transistor; and
controlling a corresponding current change in another transistor of the transconductor circuit to offset the sensed current change.
18. The method of claim 17 , wherein the another transistor of the transconductor circuit comprises a bias transistor operable to bias the transconductance transistor.
19. The method of claim 17 , wherein the controlling comprises:
feeding back a voltage to an input of the another transistor, wherein the feedback voltage is proportional to the changes in current sensed in the transconductance transistor.
20. The method of claim 17 , wherein the providing a transconductor replica feedback block comprises:
disposing a feedback transistor as a replica of the transconductance transistor.
21. The method of claim 20 , wherein the feedback transistor is configured to perform as a replica of the transconductance transistor.