Front-end system having switchable amplifier output stage

1. A method for operating a radio-frequency system, the method comprising:

obtaining a partially amplified signal from a driver stage of a power amplifier;

routing the partially amplified signal through a switch to a selected one of a plurality of output stages of the power amplifier, such that the selected output stage further amplifies the partially amplified signal;

routing the further amplified signal through a switching network for transmission from the selected output stage to a selected one of a plurality of antenna nodes, by operating the switching network such that a transmit switch couples the selected output stage to the selected antenna node; and

routing a received signal from an antenna node among the plurality of antenna nodes through the switching network, and amplifying the received signal, the routing of the further amplified signal for transmission and the routing of the received signal performed in a time-division duplexing mode.

2. The method of claim 1 wherein the routing of the partially amplified signal includes operating the switch such that an input pole of the switch is coupled to the driver stage, and a selected throw of the switch is coupled to the selected output stage.

3. The method of claim 1 wherein the routing of the further amplified signal occurs during a transmit portion of the time-division duplexing mode.

4. The method of claim 1 wherein the routing of the received signal occurs during a receive portion of the time-division duplexing mode.

5. The method of claim 4 wherein the routing of the received signal includes operating the switching network such that all of the transmit switches corresponding to the plurality of output stages are in an OFF state during the receive portion of the time-division duplexing mode.

6. The method of claim 1 wherein the routing of the received signal includes operating the switching network such that a receive switch couples the antenna node to a low-noise amplifier for the amplifying of the received signal.

7. The method of claim 6 wherein the routing of the received signal occurs during a receive portion of the time-division duplexing mode.

8. The method of claim 6 wherein the routing of the further amplified signal occurs during a transmit portion of the time-division duplexing mode.

9. The method of claim 8 wherein the routing of the further amplified signal includes operating the switching network such that all of the receive switches corresponding to the plurality of antenna nodes are in an OFF state during the transmit portion of the time-division duplexing mode.

10. The method of claim 8 wherein the routing of the further amplified signal includes providing a shunt path to a ground for each of the plurality of antenna nodes during the transmit portion of the time-division duplexing mode.

11. A front-end module comprising:

a packaging substrate configured to receive a plurality of components;

a power amplifier circuit implemented on the packaging substrate, and including a driver stage configured to generate a partially amplified signal, the power amplifier circuit further including a plurality of output stages and a switch configured to route the partially amplified signal from the driver stage to a selected one of the plurality of output stages, such that the selected output stage further amplifies the partially amplified signal; and

a switching network implemented on the packaging substrate and configured to route the further amplified signal for transmission from the selected output stage to a selected one of a plurality of antenna nodes through a transmit switch, the switching network further configured to route a received signal from an antenna node among the plurality of antenna nodes to a receive path for amplification, the switching network configured to support a time-division duplexing mode.

12. The front-end module of claim 11 further comprising a low-noise amplifier configured to provide the amplification of the received signal.

13. The front-end module of claim 11 wherein the power amplifier circuit and the switching network are implemented on a common semiconductor die that is mounted on the packaging substrate.

14. The front-end module of claim 11 wherein the power amplifier circuit is implemented on a first semiconductor die and the switching network is implemented on a second semiconductor die, each of the first and second semiconductor die mounted on the packaging substrate.

15. The front-end module of claim 11 wherein at least some of the switching network is implemented as a network of field-effect transistor switches.

16. A wireless device comprising:

a transceiver;

a plurality of antennas;

a power amplifier circuit in communication with the transceiver, and including a driver stage configured to generate a partially amplified signal, the power amplifier circuit further including a plurality of output stages and a switch configured to route the partially amplified signal from the driver stage to a selected one of the plurality of output stages, such that the selected output stage further amplifies the partially amplified signal; and

a switching network configured to route the further amplified signal for transmission from the selected output stage to a selected one of the plurality of antennas through a transmit switch, the switching network further configured to route a received signal from an antenna among the plurality of antennas to a receive path for amplification, the switching network configured to support a time-division duplexing mode.

17. The wireless device of claim 16 further comprising a low-noise amplifier configured to provide the amplification of the received signal.

18. The wireless device of claim 16 wherein the wireless device is a cellular phone.

19. The wireless device of claim 16 wherein the wireless device is configured to further provide a frequency-division duplexing mode.