Radio frequency amplifiers with an injection-locked oscillator driver stage and a stacked output stage

Abstract

Radio frequency (RF) amplifiers, such as power amplifiers, are provided herein. In certain configurations, an RF amplifier includes an input terminal that receives an RF input signal, an output terminal that provides an RF output signal, an injection-locked oscillator driver stage that amplifies the RF input signal to generate an injection-locked RF signal, and a stacked output stage that further amplifies the injection-locked RF signal to generate the RF output signal. The stacked output stage includes a stack of at least a first transistor and a second transistor in series with one another. Thus, the stacked output stage is operable over a wide range of supply voltage to overcome the relatively low breakdown voltages of scaled transistors. Moreover, the injection-locked oscillator driver stage provides the RF amplifier with excellent power efficiency, including in applications in which the stacked output stage operates with a supply voltage that is variable.

1 . (canceled) 
     
     
         2 . A multi-mode radio frequency 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; and   a stacked output stage configured to amplify the injection-locked radio frequency signal to generate a radio frequency output signal, the stacked output stage including a first field-effect transistor and a second field-effect transistor in series with one another, the stacked output stage further including a multi-throw switch configured to provide the injection-locked radio frequency signal to a gate of the first field-effect transistor in a first mode of the multi-mode radio frequency amplifier, and to provide the injection-locked radio frequency signal to a gate of the second field-effect transistor in a second mode of the multi-mode radio frequency amplifier.   
     
     
         3 . The multi-mode radio frequency amplifier of  claim 2  wherein the stacked output stage further includes a matching switch and a capacitor, the matching switch configured to connect a first end of the capacitor to the gate of the second field-effect transistor in the second mode, and to disconnect the first end of the capacitor from the gate of the second field-effect transistor in the first mode. 
     
     
         4 . The multi-mode radio frequency amplifier of  claim 3  wherein a second end of the capacitor is electrically connected to a source of the second field-effect transistor. 
     
     
         5 . The multi-mode radio frequency amplifier of  claim 2  wherein the stacked output stage further includes a third field-effect transistor in series with the first field-effect transistor and the second field-effect transistor. 
     
     
         6 . The multi-mode radio frequency amplifier of  claim 2  wherein in the first mode the first field-effect transistor operates as a common source transistor and the second field-effect transistor operates as a common gate transistor. 
     
     
         7 . The multi-mode radio frequency amplifier of  claim 2  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. 
     
     
         8 . The multi-mode radio frequency amplifier of  claim 2  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. 
     
     
         9 . The multi-mode radio frequency amplifier of  claim 8  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 . The multi-mode radio frequency amplifier of  claim 8  wherein the injection-locked oscillator further includes an output transformer configured to generate the injection-locked radio frequency signal at the output of the driver stage. 
     
     
         11 . A method of radio frequency signal amplification, the method comprising:
 receiving a radio frequency input signal as an input to a multi-mode radio frequency amplifier having a driver stage and a stacked output stage;   generating an injection-locked radio frequency signal based on the radio frequency input signal using an injection-locked oscillator of the driver stage;   amplifying the injection-locked radio frequency signal using a transistor stack of the stacked output stage, the transistor stack including at least a first field-effect transistor and a second field-effect transistor in series with one another; and   operating the stacked output stage in a selected mode of the multi-mode radio frequency amplifier chosen from at least a first mode and a second mode, including using a multi-throw switch to provide the injection-locked radio frequency signal to a gate of the first field-effect transistor in the first mode, and to provide the injection-locked radio frequency signal to a gate of the second field-effect transistor in the second mode.   
     
     
         12 . The method of  claim 11  wherein the stacked output stage further includes a matching switch and a capacitor, the method further including connecting a first end of the capacitor to the gate of the second field-effect transistor in the second mode, and disconnecting the first end of the capacitor from the gate of the second field-effect transistor in the first mode. 
     
     
         13 . The method of  claim 12  wherein a second end of the capacitor is electrically connected to a source of the second field-effect transistor. 
     
     
         14 . The method of  claim 11  further comprising operating the first field-effect transistor as a common source transistor and the second field-effect transistor as a common gate transistor in the first mode. 
     
     
         15 . A mobile device comprising:
 a transceiver configured to generate a radio frequency input signal;   an antenna configured to transmit a radio frequency output signal; and   a front end system including a multi-mode power amplifier including a driver stage and a stacked output stage, the driver stage including an injection-locked oscillator configured to receive the radio frequency input signal and to generate an injection-locked radio frequency signal, the stacked output stage configured to amplify the injection-locked radio frequency signal to generate the radio frequency output signal and including a first field-effect transistor and a second field-effect transistor in series with one another, the stacked output stage further including a multi-throw switch configured to provide the injection-locked radio frequency signal to a gate of the first field-effect transistor in a first mode of the multi-mode power amplifier, and to provide the injection-locked radio frequency signal to a gate of the second field-effect transistor in a second mode of the multi-mode power amplifier.   
     
     
         16 . The mobile device of  claim 15  wherein the stacked output stage further includes a matching switch and a capacitor, the matching switch configured to connect a first end of the capacitor to the gate of the second field-effect transistor in the second mode, and to disconnect the first end of the capacitor from the gate of the second field-effect transistor in the first mode. 
     
     
         17 . The mobile device of  claim 16  wherein a second end of the capacitor is electrically connected to a source of the second field-effect transistor. 
     
     
         18 . The mobile device of  claim 15  wherein the stacked output stage further includes a third field-effect transistor in series with the first field-effect transistor and the second field-effect transistor. 
     
     
         19 . The mobile device of  claim 15  wherein in the first mode the first field-effect transistor operates as a common source transistor and the second field-effect transistor operates as a common gate transistor. 
     
     
         20 . The mobile device of  claim 15  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. 
     
     
         21 . The mobile device of  claim 15  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.