High efficiency doherty amplifier with a segmented main amplifier

1. A Doherty power amplifier comprising:

a main amplifier device comprising a plurality of independently controllable amplifier segments;

an auxiliary amplifier device;

a coupler for coupling an input signal to each of the main amplifier device and the auxiliary amplifier device; and

a single impedance inverter for power combining an output signal of the main amplifier device with an output signal of the auxiliary amplifier device,

wherein output signals of the controllable amplifier segments are combined at an input of the impedance inverter, and

wherein the output signal of the main amplifier device and the output signal of the auxiliary amplifier device are power combined at an output of the impedance inverter.

2. The Doherty power amplifier of claim 1 , wherein the plurality of independently controllable amplifier segments comprises two independently controllable amplifier segments.

3. The Doherty power amplifier of claim 1 , wherein the input signal coupled to each of the main amplifier device and the auxiliary amplifier device comprises a single carrier signal that varies in amplitude.

4. The Doherty power amplifier of claim 1 , wherein the input signal coupled to each of the main amplifier device and the auxiliary amplifier device comprises a multi-carrier signal.

5. The Doherty power amplifier of claim 1 , wherein at least one of the main amplifier device and the auxiliary amplifier device includes a field effect transistor.

6. The Doherty power amplifier of claim 5 , wherein the plurality of independently controllable amplifier segments include:

a first independently controllable segment having a size substantially equal to W/γ, wherein W is a gate periphery of the main amplifier device and γ is a backoff design parameter; and

a second independently controllable segment having a size substantially equal to W(γ−1)/γ, wherein W is the gate periphery of the main amplifier device and γ is the backoff design parameter.

7. The Doherty power amplifier of claim 1 , wherein at least one of the main amplifier device and the auxiliary amplifier device includes a bipolar junction transistor.

8. The Doherty power amplifier of claim 7 , wherein the plurality of independently controllable amplifier segments include:

a first independently controllable segment having a size substantially equal to A/γ, wherein A is an emitter area of the main amplifier device and γ is a backoff design parameter; and

a second independently controllable segment having a size substantially equal to A(γ−1)/γ, wherein A is the emitter area of the main amplifier device and γ is the backoff design parameter.

9. The Doherty power amplifier of claim 1 , further comprising a bias controller coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of the respective one of the plurality of the independently controllable amplifier segments.

10. The Doherty power amplifier of claim 9 , wherein the bias controller is configured to turn the respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

11. The Doherty power amplifier of claim 1 , further comprising a switching control means coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of a respective one of the plurality of the independently controllable amplifier segments.

12. The Doherty power amplifier of claim 11 , wherein the switching control means is configured to turn a respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

13. The Doherty power amplifier of claim 9 , wherein the bias controller is configured to supply an ON bias voltage to turn on the one of the independently controllable amplifier segments.

14. The Doherty power amplifier of claim 9 , wherein the bias controller is configured to supply an OFF bias voltage to the one of the independently controllable amplifier segments for a range of output power below a predefined power transition point.

15. The Doherty power amplifier of claim 1 , wherein the impedance inverter is a transmission line configured to provide a 90° phase shift to at least one of the output signal of the main amplifier device and the output signal of the auxiliary amplifier device.

16. The Doherty power amplifier of claim 1 , wherein a power transition point is determined based on an output power at which the main amplifier device saturates and at which the auxiliary amplifier device turns on.

17. A Doherty power amplifier comprising:

a main amplifier device including a plurality of independently controllable amplifier segments, the independently controllable amplifier segments having a common drain shared output;

an auxiliary amplifier device;

a coupler for coupling an input signal to each of the main amplifier device and the auxiliary amplifier device; and

a single impedance inverter for power combining an output signal of the main amplifier device with an output signal of the auxiliary amplifier device,

wherein the common drain shared output of the plurality of independently controllable amplifier segments is connected to an input of the impedance inverter, and

wherein the output signal of the main amplifier device and the output signal of the auxiliary amplifier device are power combined at an output of the impedance inverter.

18. The Doherty power amplifier of claim 17 , wherein the plurality of independently controllable amplifier segments comprises two independently controllable amplifier segments.

19. The Doherty power amplifier of claim 17 , wherein the input signal coupled to each of the main amplifier device and the auxiliary amplifier device comprises a single carrier signal that varies in amplitude.

20. The Doherty power amplifier of claim 17 , wherein the input signal coupled to each of the main amplifier device and the auxiliary amplifier device comprises a multi-carrier signal.

21. The Doherty power amplifier of claim 18 , wherein the plurality of independently controllable amplifier segments include:

a first independently controllable segment having a size substantially equal to W/γ, wherein W is a gate periphery of the main amplifier device and γ is a backoff design parameter; and

a second independently controllable segment having a size substantially equal to W(γ−1)/γ, wherein W is the gate periphery of the main amplifier device and γ is the backoff design parameter.

22. The Doherty power amplifier of claim 17 , further comprising a bias controller coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of the respective one of the plurality of the independently controllable amplifier segments.

23. The Doherty power amplifier of claim 22 , wherein the bias controller is configured to turn the respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

24. The Doherty power amplifier of claim 17 , further comprising a switching control means coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of a respective one of the plurality of the independently controllable amplifier segments.

25. The Doherty power amplifier of claim 24 , wherein the switching control means is configured to turn a respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

26. The Doherty power amplifier of claim 22 , wherein the bias controller is configured to supply an ON bias voltage to turn on the one of the independently controllable amplifier segments.

27. The Doherty power amplifier of claim 22 , wherein the bias controller is configured to supply an OFF bias voltage to the one of the independently controllable amplifier segments for a range of output power below a predefined power transition point.

28. The Doherty power amplifier of claim 17 , wherein the impedance inverter is a transmission line configured to provide a 90° phase shift to at least one of the output signal of the main amplifier device and the output signal of the auxiliary amplifier device.

29. The Doherty power amplifier of claim 17 , wherein a power transition point is determined based on an output power at which the main amplifier device saturates and at which the auxiliary amplifier device turns on.

30. A Doherty power amplifier comprising:

a main amplifier device comprising a plurality of independently controllable amplifier segments, the independently controllable amplifier segments having a common collector shared output;

an auxiliary amplifier device;

a coupler for coupling an input signal to each of the main amplifier device and the auxiliary amplifier device; and

a single impedance inverter for power combining an output signal of the main amplifier device with an output signal of the auxiliary amplifier device,

wherein the common collector shared output of the plurality of independently controllable amplifier segments is connected to an input of the impedance inverter; and

wherein the output signal of the main amplifier device and the output signal of the auxiliary amplifier device is power combined at an output of the impedance inverter.

31. The Doherty power amplifier of claim 30 , wherein the plurality of independently controllable amplifier segments comprises two independently controllable amplifier segments.

32. The Doherty power amplifier of claim 30 , wherein the input signal to each of the main amplifier device and the auxiliary amplifier device comprises a single carrier signal that varies in amplitude.

33. The Doherty power amplifier of claim 30 , wherein the input signal to each of the main amplifier device and the auxiliary amplifier device comprises a multi-carrier signal.

34. The Doherty power amplifier of claim 31 , wherein the independently controllable amplifier segments include:

a first independently controllable amplifier segment having a size substantially equal to A/γ, wherein A is an emitter area of the main amplifier device and γ is a backoff design parameter; and

a second independently controllable amplifier segment having a size substantially equal to A(γ−1)/γ, wherein A is the emitter area of the main amplifier device and γ is the backoff design parameter.

35. The Doherty power amplifier of claim 30 , further comprising a bias controller coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of the respective one of the plurality of the independently controllable amplifier segments.

36. The Doherty power amplifier of claim 35 , wherein the bias controller is configured to turn the respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

37. The Doherty power amplifier of claim 30 , further comprising a switching control means coupled to at least one of the plurality of the independently controllable amplifier segments to control a state of a respective one of the plurality of the independently controllable amplifier segments.

38. The Doherty power amplifier of claim 37 , wherein the switching control means is configured to turn a respective one of the independently controllable amplifier segments on only for a range of output powers above a predefined power transition point.

39. The Doherty power amplifier of claim 35 , wherein the bias controller is configured to supply an ON bias voltage to turn on the one of the independently controllable amplifier segments.

40. The Doherty power amplifier of claim 35 , wherein the bias controller is configured to supply an OFF bias voltage to the one of the independently controllable amplifier segments for a range of output power below a predefined power transition point.

41. The Doherty power amplifier of claim 30 , wherein the impedance inverter is a transmission line configured to provide a 90° phase shift to at least one of the output signal of the main amplifier device and the output signal of the auxiliary amplifier device.