Feedback LNA with resistor
A receiver includes a feedback low noise amplifier (LNA). The feedback LNA has an LNA gain and includes an LNA input configured to receive a signal from an antenna and an LNA output configured to output an amplified voltage signal. The receiver also includes a resistive element, having a resistance, coupled to the LNA output and configured to convert the amplified voltage signal into a current. The receiver also includes a current commuting mixer coupled to the resistive element and configured to receive the current from the resistive element, where the current output by the resistive element is determined at least in part by the amplified voltage signal and the resistance of the resistive element.
1. A receiver comprising:
a feedback low noise amplifier (LNA), having an LNA gain, and including:
an LNA input configured to receive a signal from an antenna; and
an LNA output configured to output an amplified voltage signal;
a resistive element, having a resistance, coupled to the LNA output and configured to convert the amplified voltage signal into a current; and
a current commuting mixer coupled to the resistive element and configured to receive the current from the resistive element, wherein the current output by the resistive element is to determined at least in part by the amplified voltage signal and the resistance of the resistive element.
2. The receiver of claim 1 , wherein the resistance of the resistive element is substantially within the range of 500Ω to 1 kΩ.
3. The receiver of claim 1 , wherein the feedback LNA further includes:
a feedback resistor with a resistance of Rfb; and
a gain element with a gain of A, wherein a first end of the feedback resistor is coupled to the output of the gain element and a second end of the feedback resistor is coupled to the input of the gain element.
4. The receiver of claim 3 , wherein Rfb is substantially within the range of 500Ω to 8 kΩ.
5. The receiver of claim 3 , wherein the feedback resistor has an adjustable resistance and/or the gain element has an adjustable gain.
6. The receiver of claim 3 , wherein the input impedence of the feedback LNA is approximated by Rin≈Rfb/A.
7. The receiver of claim 6 , wherein the input impedance of the feedback LNA is matched to the antenna.
8. The receiver of claim 1 , wherein power consumed by the receiver decreases as the resistance of the resistive element increases.
9. The receiver of claim 1 , wherein the feedback LNA includes:
a first transconductor having a gain of Gm 1 and a second transconductor having a gain of Gm 2 ;
a first resistor connected to ground, a second resistor, and a third resistor; and
a capacitor connected to ground, wherein:
the output of the first transconductor is connected to the capacitor, the first resistor, the input of the second transconductor, and a first end of the second resistor;
the output of the second transconductor is connected to a second end of the second resistor and a first end of the third resistor; and
a second end of the third resistor is connected to the input of the first transconductor.
10. The receiver of claim 9 , wherein Gm 1 is strictly greater than Gm 2 .
11. The receiver of claim 1 , wherein the feedback LNA includes:
a first transconductor having a gain of Gm 1 and a second transconductor having a gain of Gm 2 ;
a first resistor connected to ground, a second resistor, and a third resistor; and
a common gate transistor, wherein:
the output of the first transconductor is connected to the first resistor, a first end of the third resistor, and the source of the common gate transistor;
the drain of the common gate transistor is connected to a first end of the second resistor, and the input of the second transconductor; and
the output of the second transconductor is connected to a second end of the second transistor and a second end of the third transistor.
12. The receiver of claim 11 , wherein Gm 1 is strictly greater than Gm 2 .
13. A method comprising:
receiving a signal from an antenna;
amplifying the received signal using a feedback low noise amplifier (LNA) to generate an amplified voltage signal;
converting the amplified voltage signal into a current using a resistive element, having a resistance, wherein the current is determined at least in part by the amplified voltage signal and the resistance of the resistive element; and
outputting the current to a current commuting mixer.
14. The method of claim 13 , wherein the feedback LNA includes:
a feedback resistor with a resistance of Rfb; and
a gain element with a gain of A, wherein a first end of the feedback resistor is coupled to the output of the gain element and a second end of the feedback resistor is coupled to the input of the gain element.
15. The method of claim 14 , wherein the feedback resistor has an adjustable resistance and/or the gain element has an adjustable gain.
16. The method of claim 14 , wherein the input impedence of the feedback LNA is approximated by Rin≈Rfb/A.
17. The method of claim 16 , wherein the input impedance of the feedback LNA is matched to the antenna.
18. The method of claim 13 , wherein power consumed by the receiver decreases as the resistance of the resistive element increases.
19. The method of claim 13 , wherein the feedback LNA includes:
a first transconductor having a gain of Gm 1 and a second transconductor having a gain of Gm 2 ;
a first resistor connected to ground, a second resistor, and a third resistor; and
a capacitor connected to ground, wherein:
the output of the first transconductor is connected to the capacitor, the first resistor, the input of the second transconductor, and a first end of the second resistor;
the output of the second transconductor is connected to a second end of the second resistor and a first end of the third resistor; and
a second end of the third resistor is connected to the input of the first transconductor.
20. The method of claim 13 , wherein the feedback LNA includes:
a first transconductor having a gain of Gm 1 and a second transconductor having a gain of Gm 2 ;
a first resistor connected to ground, a second resistor, and a third resistor; and
a common gate transistor, wherein:
the output of the first transconductor is connected to the first resistor, a first end of the third resistor, and the source of the common gate transistor;
the drain of the common gate transistor is connected to a first end of the second resistor, and the input of the second transconductor; and
the output of the second transconductor is connected to a second end of the second transistor and a second end of the third transistor.