Abstract: Aspects of this disclosure relate to an amplification circuit that includes a stacked amplifier and a bias circuit. The stacked amplifier includes at least a first transistor and a second transistor in series with each other. The stacked amplifier is operable in at least a first mode and a second mode. The bias circuit is configured to bias the second transistor to a linear region of operation in the first mode and to bias the second transistor as a switch in the second mode. In certain embodiments, the amplification circuit can be a power amplifier stage configured to receive a supply voltage that has a different voltage level in the first mode than in the second mode.

Abstract: Front end systems and related devices, integrated circuits, modules, and methods are disclosed. One such front end system includes a low noise amplifier in a receive path and a multi-mode power amplifier circuit in a transmit path. The low noise amplifier includes a first inductor, an amplification circuit, and a second inductor magnetically coupled to the first inductor to provide negative feedback to linearize the low noise amplifier. The multi-mode power amplifier circuit includes a stacked output stage including a transistor stack of two or more transistors. The multi-mode power amplifier circuit also includes a bias circuit configured to control a bias of at least one transistor of the transistor stack based on a mode of the multi-mode power amplifier circuit. Other embodiments of front end systems are disclosed, along with related devices, integrated circuits, modules, methods, and components thereof.

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.

Abstract: Apparatus and methods for power amplifiers with an injection-locked oscillator driver stage are provided herein. In certain configurations, a multi-mode power amplifier includes a driver stage implemented using an injection-locked oscillator and an output stage having an adjustable supply voltage that changes based on a mode of the multi-mode power amplifier. By implementing the multi-mode power amplifier in this manner, the multi-mode power amplifier exhibits excellent efficiency, including when the voltage level of the adjustable supply voltage is relatively low.

Abstract: Aspects of this disclosure relate to an amplification circuit that includes a stacked amplifier and a bias circuit. The stacked amplifier includes at least a first transistor and a second transistor in series with each other. The stacked amplifier is operable in at least a first mode and a second mode. The bias circuit is configured to bias the second transistor to a linear region of operation in the first mode and to bias the second transistor as a switch in the second mode. In certain embodiments, the amplification circuit can be a power amplifier stage configured to receive a supply voltage that has a different voltage level in the first mode than in the second mode.