Apparatus and method for improving efficiency in power amplifier

1. An apparatus for power amplification, the apparatus comprising:

a controller for selecting a power amplifier among a Doherty power amplifier and a supply modulated amplifier;

the Doherty power amplifier for amplifying a power of a transmission signal when the Doherty power amplifier is selected by the controller; and

the supply modulated amplifier for amplifying the power of the transmission signal using a supply voltage determined considering an amplitude of the transmission signal when the supply modulated amplifier is selected by the controller.

2. The apparatus of claim 1 , wherein the Doherty power amplifier and the supply modulated amplifier are connected in parallel.

3. The apparatus of claim 1 , wherein the controller selects a power amplifier for amplifying the power of the transmission signal among the Doherty power amplifier and the supply modulated amplifier based on an output power of the transmission signal.

4. The apparatus of claim 1 , wherein, when an output power of a transmission signal is greater than a reference power, the controller selects the supply modulated amplifier to amplify the transmission signal, and

when the output power of the transmission signal is less than the reference power, the controller selects the Doherty power amplifier to amplify the transmission signal.

5. The apparatus of claim 1 , wherein the supply modulated amplifier comprises one of an Envelope Elimination and Restoration (EER) power amplifier, an Envelope Tracking (ET) power amplifier, and a polar power amplifier.

6. The apparatus of claim 1 , wherein the supply modulated amplifier comprises:

a supply modulator for generating a supply voltage of a power amplifier considering the amplitude of the transmission signal; and

the power amplifier for amplifying a power of the transmission signal based on the supply voltage of the power amplifier generated in the supply modulator.

7. The apparatus of claim 1 , wherein the Doherty power amplifier comprises a carrier amplifier and a peaking amplifier.

8. The apparatus of claim 7 , wherein the carrier amplifier and the peaking amplifier comprise power cells of different levels.

9. The apparatus of claim 1 , further comprising:

an output power controller for comparing an output power of the transmission signal with a reference power, and for generating a power mode control signal for selecting a power amplifier among the Doherty power amplifier and the supply modulated amplifier,

wherein the controller selects a power amplifier among the Doherty power amplifier and the supply modulated amplifier based on the power mode control signal generated in the output power controller.

10. The apparatus of claim 1 , wherein the controller controls bias circuits of the Doherty power amplifier and the supply modulated amplifier, and selects the power amplifier for amplifying the transmission signal.

11. The apparatus of claim 10 , wherein, when the supply modulated amplifier is selected to amplify the power of the transmission signal, the controller controls the bias circuits of the Doherty power amplifier and the supply modulated amplifier to activate the supply modulated amplifier and to deactivate the Doherty power amplifier, and

when the Doherty power amplifier is selected to amplify the power of the transmission signal, the controller controls the bias circuits of the Doherty power amplifier and the supply modulated amplifier to activate the Doherty power amplifier and to deactivate the supply modulated amplifier.

12. The apparatus of claim 1 , wherein the controller provides the transmission signal as an input signal to one power amplifier among the Doherty power amplifier and the supply modulated amplifier, based on an output power of the transmission signal.

13. The apparatus of claim 12 , wherein, when the supply modulated amplifier is selected to amplify the power of the transmission signal, the controller controls to provide the transmission signal as the input signal to the supply modulated amplifier and to amplify the transmission signal using the supply modulated amplifier, and

when the Doherty power amplifier is selected to amplify the power of the transmission signal, the controller controls to provide the transmission signal as the input signal to the Doherty power amplifier and to amplify the transmission signal using the Doherty power amplifier.

14. The apparatus of claim 1 , wherein the controller selects the power amplifier among the Doherty power amplifier and the supply modulated amplifier based on whether an output power of the transmission signal is greater than a reference power.

15. A method for amplifying a power of a transmission signal in a transmit end of a wireless communication system comprising a Doherty power amplifier and a supply modulated amplifier, the method comprising:

selecting a power amplifier for amplifying a power of a transmission signal among the Doherty power amplifier and the supply modulated amplifier; and

amplifying the power of the transmission signal using the selected power amplifier.

16. The method of claim 15 , wherein the Doherty power amplifier and the supply modulated amplifier are connected in parallel.

17. The method of claim 15 , wherein the selecting of the power amplifier comprises:

selecting a power amplifier for amplifying the power of the transmission signal among the Doherty power amplifier and the supply modulated amplifier, based on an output power of the transmission signal.

18. The method of claim 17 , wherein the selecting of the power amplifier comprises:

when the output power of the transmission signal is greater than a reference power, selecting the supply modulated amplifier, and

when the output power of the transmission signal is less than the reference power, selecting the Doherty power amplifier.

19. The method of claim 15 , wherein the supply modulated amplifier comprises:

one of an Envelope Elimination and Restoration (EER) power amplifier, an Envelope Tracking (ET) power amplifier, and a polar power amplifier.

20. The method of claim 15 , wherein the supply modulated amplifier comprises:

a supply modulator for generating a supply voltage of a power amplifier considering the amplitude of the transmission signal; and

the power amplifier for amplifying the power of the transmission signal based on the supply voltage of the power amplifier generated in the supply modulator.

21. The method of claim 15 , wherein the Doherty power amplifier comprises a carrier amplifier and a peaking amplifier.

22. The method of claim 21 , wherein the carrier amplifier and the peaking amplifier comprise power cells of different levels.

23. The method of claim 15 , wherein the amplifying of the power of the transmission signal comprises:

when the supply modulated amplifier is selected, controlling a bias circuit of the supply modulated amplifier to activate the supply modulated amplifier and controlling a bias circuit of the Doherty power amplifier to deactivate the Doherty power amplifier; and

amplifying the power of the transmission signal using the supply modulated amplifier.

24. The method of claim 15 , wherein the amplifying of the power of the transmission signal comprises:

when the Doherty power amplifier is selected, controlling a bias circuit of the Doherty power amplifier to activate the Doherty power amplifier and controlling a bias circuit of the supply modulated amplifier to deactivate the envelope tracking power amplifier; and

amplifying the power of the transmission signal using the Doherty power amplifier.

25. The method of claim 15 , wherein the amplifying of the power of the transmission signal comprises:

when the supply modulated amplifier is selected, providing the transmission signal to the supply modulated amplifier; and

amplifying the power of the transmission signal using the supply modulated amplifier.

26. The method of claim 15 , wherein the amplifying of the power of the transmission signal comprises:

when the Doherty power amplifier is selected, providing the transmission signal to the Doherty power amplifier; and

amplifying the power of the transmission signal using the Doherty power amplifier.

27. The method of claim 15 , wherein the amplifying of the power of the transmission signal comprises:

when the supply modulated amplifier is selected, determining an amplitude of the transmission signal;

generating a supply voltage of the power amplifier based on the amplitude of the transmission signal; and

amplifying the power of the transmission signal based on the supply voltage.

28. The method of claim 15 , wherein the selecting of the power amplifier comprises,

selecting the power amplifier among the Doherty power amplifier and the supply modulated amplifier based on whether an output power of the transmission signal is greater than a reference power.