Apparatus and methods for power amplifiers with an injection-locked oscillator driver stage

1. A multi-mode power amplifier comprising:

a driver stage including an injection-locked oscillator configured to receive a radio frequency input signal and to generate an injection-locked radio frequency signal;

an output stage configured to amplify the injection-locked radio frequency signal to generate a radio frequency output signal, the output stage configured to receive power from an adjustable supply voltage; and

a supply control circuit configured to control a voltage level of the adjustable supply voltage based on a mode of the multi-mode power amplifier.

2. The multi-mode power amplifier of claim 1 wherein the injection-locked oscillator includes an output balun configured to provide a differential to singled-ended signal conversion.

3. The multi-mode power amplifier of claim 1 wherein the driver stage is powered by a substantially fixed supply voltage.

4. The multi-mode power amplifier of claim 3 wherein the mode of the multi-mode power amplifier is selectable between two or more power modes including a high power mode in which the adjustable supply voltage is greater than the substantially fixed supply voltage and a low power mode in which the adjustable supply voltage is less than the substantially fixed supply voltage.

5. The multi-mode power amplifier of claim 1 wherein the radio frequency input signal is a modulated signal having a substantially constant signal envelope.

6. The multi-mode power amplifier of claim 1 wherein the radio frequency input signal is a single-ended input signal, and the injection-locked oscillator includes an input transformer configured to convert the single-ended input signal to a differential input signal.

7. The multi-mode power amplifier of claim 1 wherein the injection-locked oscillator includes a negative transconductance circuit electrically connected to an inductor-capacitor tank, the negative transconductance circuit configured to provide energy to the inductor-capacitor tank to maintain oscillations.

8. The multi-mode power amplifier of claim 7 wherein the negative transconductance circuit includes a pair of cross-coupled field-effect transistors.

9. The multi-mode power amplifier of claim 7 wherein the injection-locked oscillator further includes a signal injecting circuit configured to provide signal injection to the inductor-capacitor tank based on the radio frequency input signal.

10. A method of radio frequency signal amplification, the method comprising:

generating an injection-locked radio frequency signal from a radio frequency input signal using an injection-locked oscillator of a multi-mode power amplifier;

amplifying the injection-locked radio frequency signal using an output stage of the multi-mode power amplifier;

powering the output stage using an adjustable supply voltage; and

controlling a voltage level of the adjustable supply voltage based on a mode of the multi-mode power amplifier using a supply control circuit.

11. The method of claim 10 further comprising providing a differential to singled-ended signal conversion at an output of the driver stage using an output balun.

12. The method of claim 10 further comprising powering the driver stage using a substantially fixed supply voltage.

13. The method of claim 10 further comprising providing a modulated signal having a substantially constant signal envelope to an input of the driver stage.

14. The method of claim 10 further comprising injection locking an inductor-capacitor tank of the injection-locked oscillator to the radio frequency input signal.

15. The method of claim 14 further comprising providing energy to the inductor-capacitor tank to maintain oscillations using a negative transconductance circuit.

16. A packaged module comprising:

a package substrate; and

a semiconductor die attached to the package substrate, the semiconductor die including a multi-mode power amplifier including a driver stage including an injection-locked oscillator configured to receive a radio frequency input signal and to generate an injection-locked radio frequency signal, and an output stage configured to amplify the injection-locked radio frequency signal to generate a radio frequency output signal, the output stage configured to receive power from an adjustable supply voltage having a voltage level that changes based on a mode of the multi-mode power amplifier.

17. The packaged module of claim 16 wherein the semiconductor die further includes a low noise amplifier and a switch electrically connected to the low noise amplifier and to the multi-mode power amplifier.

18. The packaged module of claim 16 wherein the injection-locked oscillator includes a negative transconductance circuit electrically connected to an inductor-capacitor tank, the negative transconductance circuit configured to provide energy to the inductor-capacitor tank to maintain oscillations.

19. The packaged module of claim 18 wherein the injection-locked oscillator further includes a signal injecting circuit configured to provide signal injection to the inductor-capacitor tank based on the radio frequency input signal.

20. The packaged module of claim 16 wherein the semiconductor die is a silicon-on-insulator die.