Low-noise amplifier with impedance boosting circuit

1. A low-noise amplifier having an input terminal and an output terminal, the low-noise amplifier comprising:

an input circuit configured to operate with a variable bias current, the input circuit comprising:

a transistor having a gate electrically connected to a gate inductor and a source electrically connected to a source inductor, wherein the gate inductor is electrically connected to the input terminal; and

an impedance boosting circuit electrically connected to the source inductor, the impedance boosting circuit comprising:

at least two switches comprising at least two switch transistors controlled by a control signal that varies the total inductance of the impedance boosting circuit and thereby varies the input impedance of the low-noise amplifier; and

at least two tail inductors electrically connected with the at least two switches, the at least two tail inductors for increasing the input impedance of the low-noise amplifier when the impedance boosting circuit is activated via the at least two switches; and

wherein the low-noise amplifier is configured to activate the impedance boosting circuit if the variable bias current is reduced.

2. The low-noise amplifier of claim 1 , wherein each tail inductor of the at least two tail inductors is connected in parallel with a corresponding switch of the at least two switches.

3. The low-noise amplifier of claim 2 , wherein the control signal activates and de-activates the impedance boosting circuit and thereby varies the input impedance of the low-noise amplifier.

4. The low-noise amplifier of claim 1 , wherein the low-noise amplifier is configured as a single-ended amplifier and the transistor includes a drain electrically connected to the output terminal of the low-noise amplifier if the low noise amplifier is a single-stage amplifier or to a second stage if the amplifier is a multi-stage amplifier.

5. The low-noise amplifier of claim 1 , wherein the low-noise amplifier is configured as a differential amplifier comprising:

two input circuits, the two input circuits each comprising a transistor, a gate inductor, and a source inductor; and

two impedance boosting circuits, wherein the source inductors of the two input circuits are electrically connected to one of the two impedance boosting circuits, respectively.

6. The low-noise amplifier of claim 1 , wherein the low-noise amplifier is configured as a differential amplifier comprising:

two input circuits, the two input circuits each comprising a transistor, a gate inductor, and a source inductor; and

wherein the impedance boosting circuit is electrically connected to each of the source inductors of the two input circuits.

7. A low-noise amplifier configured as a differential amplifier comprising:

two input circuits, the two input circuits each comprising a transistor having a gate electrically connected to a gate inductor and a source electrically connected to a source inductor, wherein the gate inductor is electrically connected to an input terminal, wherein each input circuit is configured to operate with a variable bias current; and

an impedance boosting circuit electrically connected to the source inductors, the impedance boosting circuit comprising:

two branches of tail inductors, each branch comprising at least two tail inductors electrically connected in series; and

at least two switch transistors electrically connected to both the two branches of tail inductors and configured to be controlled by a control signal that thereby varies the input impedance of the low-noise amplifier,

wherein the low-noise amplifier is configured to activate the impedance boosting circuit if the variable bias current is reduced.

8. The low-noise amplifier of claim 7 , wherein each branch of the tail inductors further comprises a third tail inductor electrically connected to a third switch transistor.

9. The low-noise amplifier of claim 8 , wherein the two third tail inductors are configured as a differential inductor.

10. The low-noise amplifier of claim 1 , wherein the low-noise amplifier is further configured to deactivate the impedance boosting circuit if the variable bias current is increased.

11. The low-noise amplifier of claim 1 , wherein the low-noise amplifier is further configured to reduce the variable bias current if an input signal amplitude is above a predetermined value.

12. The low-noise amplifier of claim 1 , wherein the inductance of the at least two tail inductors is selected such that the input impedance of the low-noise amplifier matches the output impedance of a circuit electrically connected to an input terminal of the low-noise amplifier when the impedance boosting circuit is activated.

13. The low-noise amplifier of claim 1 , wherein:

the low-noise amplifier is configured to selectively operate in at least a high-performance mode and a low-performance mode;

a bias current for the high-performance mode is higher than a bias current for the low-performance mode; and

the low-noise amplifier is configured to activate the impedance boosting circuit if operating in the low-performance mode and deactivate the impedance boosting circuit if operating in the high-performance mode.

14. The low-noise amplifier of claim 1 , wherein the low-noise amplifier further comprises a control unit configured to provide a one-bit or a multi-bit control signal, to control the impedance boosting circuit.

15. A circuit arrangement, comprising:

a low-noise amplifier having an input terminal and an output terminal and comprising:

an input circuit configured to operate with a variable bias current, the input circuit comprising:

a transistor having a gate electrically connected to a gate inductor and a source electrically connected to a source inductor, wherein the gate inductor is electrically connected to the input terminal; and

an impedance boosting circuit electrically connected to the source inductor, the impedance boosting circuit comprising:

at least one switch; and

at least one tail inductor electrically connected with the at least one switch, the at least one tail inductor for increasing the input impedance of the low-noise amplifier when the impedance boosting circuit is activated via the at least one switch; and

an RF front end stage configured to provide an input signal to the input terminal of the low-noise amplifier and comprising a radio frequency front end comprising a radio frequency filter, the radio frequency filter having an output impedance; and

wherein the low-noise amplifier is configured to activate the impedance boosting circuit if the variable bias current is reduced, and the at least one tail inductor is configured to increase the input impedance of the low-noise amplifier when the impedance boosting circuit is activated such that the input impedance of the low-noise amplifier matches the output impedance of the radio frequency filter.

16. A method of impedance matching a low-noise amplifier with another electrical circuit, wherein the low-noise amplifier comprises an input circuit and an impedance boosting circuit and the method comprises:

inputting an electrical signal into the input circuit, the input circuit configured to operate with a variable bias current and comprising a transistor having a gate electrically connected to a gate inductor and a source electrically connected to a source inductor, wherein the electrical signal inputs to the gate inductor;

operating the input circuit with the variable bias current by selectively operating the low-noise amplifier in at least a high-performance mode and a low-performance mode, wherein a bias current for the high-performance mode is higher than a bias current for the low-performance mode;

reducing the variable bias current; and

activating the impedance boosting circuit if operating in the low-performance mode and de-activating the impedance boosting circuit if operating in the high performance mode, wherein the impedance boosting circuit is electrically connected to the source inductor and comprises:

at least one switch; and

at least one tail inductor electrically connected with the at least one switch, the at least one tail inductor configured to increase the input impedance of the low-noise amplifier when the impedance boosting circuit is activated via the at least one switch.

17. The method of claim 16 , further comprising:

determining the signal strength of the electrical signal; and

based on the determined signal strength, selecting the high-performance mode or the low-performance mode as the operating mode of the low-noise amplifier.

18. The method of claim 17 , further comprising:

determining if the selected operating mode is the current operating mode;

if the selected operating mode is different from the current operating mode, changing the operating mode to the selected operating mode.

19. A mobile terminal comprising the low-noise amplifier of claim 1 .

20. A mobile terminal comprising the low-noise amplifier of claim 7 .

21. A mobile terminal, comprising the circuit arrangement of claim 15 .

22. A mobile terminal comprising a low-noise amplifier configured to match impedance with another electrical circuit, the low-noise amplifier comprising:

an input circuit configured to operate with a variable bias current and comprising a transistor having a gate electrically connected to a gate inductor and a source electrically connected to a source inductor, wherein an electrical signal inputs to the gate inductor;

an impedance boosting circuit electrically connected to the source inductor and comprising:

at least one switch; and

at least one tail inductor electrically connected with the at least one switch, the at least one tail inductor configured to increase the input impedance of the low-noise amplifier when the impedance boosting circuit is activated via the at least one switch; and

a control circuit configured to:

input the electrical signal to the input circuit;

operate the input circuit with the variable bias current by selectively operating the low-noise amplifier in at least a high-performance mode and a low-performance mode, wherein a bias current for the high-performance mode is higher than a bias current for the low-performance mode;

reduce the variable bias current; and

activate the impedance boosting circuit if operating in the low-performance mode and de-activate the impedance boosting circuit if operating in the high performance mode.

23. The mobile terminal of claim 22 , wherein the control circuit is configured to:

determine the signal strength of the electrical signal; and

based on the determined signal strength, select the high-performance mode or the low-performance mode as the operating mode of the low-noise amplifier.

24. The mobile terminal of claim 23 , wherein the control circuit is configured to:

determine if the selected operating mode is the current operating mode; and

if the selected operating mode is different from the current operating mode, change the operating mode to the selected operating mode.