Method and apparatus of an input resistance of a passive mixer to broaden the input matching bandwidth of a common source/gate LNA
View Patent ↗A common-source Low Noise Amplifier (LNA) comprises a first spiral inductor coupled to a source of a first transistor, a second spiral inductor coupled to a drain of a second transistor, and a third inductor connecting the first transistor to the second transistor. The third inductor is configurable to enable a first capacitance to be coupled in parallel to form a bandpass filter. The first spiral inductor is configurable to enable a second capacitance to be coupled in parallel to form a resonant circuit. A variation of the LNA further includes a drain of a third transistor coupled to a gate of a fourth transistor with a first width, a source of the third transistor coupled to the resonant circuit, and an oscillator clock configured to operate at a first frequency that enables the third transistor, wherein the third transistor presents a first impedance to the resonant circuit, causing the resonant circuit to have a first bandwidth.
1. A common-source Low Noise Amplifier (LNA), comprising:
a first spiral inductor coupled to a source of a first transistor;
a second spiral inductor coupled to a drain of a second transistor; and
a third inductor connecting the first transistor to the second transistor, wherein the first spiral inductor is configurable to enable a first capacitance to be coupled in parallel to form a resonant circuit.
2. The common-source LNA of claim 1 , wherein the third inductor is configurable to enable a second capacitance to be coupled in parallel to form a bandpass filter.
3. The common-source LNA of claim 1 , wherein the resonant circuit oscillates at a lower frequency than a center frequency when a width of the second transistor is less than a width of the first transistor.
4. The common-source LNA of claim 1 , wherein the resonant circuit oscillates at a higher frequency than a center frequency when a width of the second transistor is greater than a width of the first transistor.
5. The common-source LNA of claim 1 , further comprising:
a drain of a third transistor coupled to a gate of a fourth transistor with a first width;
a source of the third transistor configured to be coupled to the resonant circuit; and
an oscillator clock configured to operate at a first frequency that enables the third transistor,
wherein the third transistor presents a first impedance to the resonant circuit, causing the resonant circuit to have a first bandwidth.
6. The common-source LNA of claim 5 , wherein the resonant circuit has a wider bandwidth than the first bandwidth when either a frequency of the oscillator clock is larger than the first frequency, a width of the fourth transistor is larger than the first width, or both are increased simultaneously.
7. The common-source LNA of claim 5 , wherein the resonant circuit has a narrower bandwidth than the first bandwidth when either a frequency of the oscillator clock is less than the first frequency, a width of the fourth transistor is less than the first width, or both are decreased simultaneously.
8. A method for making a common-source LNA, comprising:
coupling a first spiral inductor to a source of a first transistor;
coupling a second spiral inductor to a drain of a second transistor;
connecting a third inductor between the first transistor and the second transistor; and
configuring the first spiral inductor to enable coupling a first capacitance in parallel, thereby forming a resonant circuit.
9. The method of claim 8 , further comprising:
configuring the third inductor to enable coupling a second capacitance in parallel, thereby forming a bandpass filter.
10. The method of claim 8 , wherein the resonant circuit oscillates at a lower frequency than a center frequency when a width of the second transistor is less than a width of the first transistor.
11. The method of claim 8 , wherein the resonant circuit oscillates at a higher frequency than a center frequency when a width of the second transistor is greater than a width of the first transistor.
12. The method of claim 8 , further comprising:
coupling a drain of a third transistor to a gate of a fourth transistor with a first width;
coupling a source of the third transistor to the resonant circuit;
configuring an oscillator clock to operate at a first frequency to enable the third transistor; and
presenting a first impedance of the third transistor to the resonant circuit, causing the resonant circuit to have a first bandwidth.
13. The method of claim 12 , wherein the resonant circuit has a wider bandwidth than the first bandwidth when either a frequency of the oscillator clock is larger than the first frequency, a width of the fourth transistor is larger than the first width, or both are increased simultaneously.
14. The method of claim 12 , wherein the resonate circuit has a narrower bandwidth than the first bandwidth when either a frequency of the oscillator clock is less than the first frequency, a width of the fourth transistor is less than the first width, or both are decreased simultaneously.
15. The method of claim 12 , wherein energy from the resonant circuit is used to charge the gate of the fourth transistor.