Power amplifier having selective signal paths. In some embodiments, a power amplifier circuit can include a plurality of signal paths sharing a common amplification stage configured to partially amplify a signal. Each signal path can further include a dedicated amplification stage coupled to the common amplification stage and configured to be capable of further amplifying the partially amplified signal. The power amplifier circuit can further include a bias selector having a switch configured to provide a bias signal to a selected dedicated amplification stage among the plurality of signal paths to thereby allow the selected dedicated amplification stage to further amplify the partially amplified signal.

Described examples include multistage amplifier circuits having first and second forward circuits, a comparator or sensor circuit coupled to sense a signal in the second forward circuit to identify nonlinear operation or slewing conditions in the multistage amplifier circuit, and one or more sample hold circuits operative according to a sensor circuit output signal to selectively maintain the amplitude of an amplifier input signal in the second forward circuit and/or in a feedback circuit in response to the sensor circuit output signal indicating nonlinear operation or slewing conditions in the multistage amplifier circuit. Certain examples further include a clamping circuit operative to selectively maintain a voltage at a terminal of a Miller compensation capacitance responsive to the comparator output signal indicating nonlinear operation or slewing conditions.

Various embodiments of switched amplifiers are disclosed herein. In some embodiments, a switched amplifier may include a first amplifier; a second amplifier; an input matching network common to both the first and second amplifiers; and at least one switch to couple an input of the switched amplifier, via the input matching network, to one of the first amplifier or the second amplifier. In some embodiments, a switched amplifier may include a first amplifier; a second amplifier; an input matching network common to both the first and second amplifiers or an output matching network common to both the first and second amplifiers; and a bias generation circuit to selectively (1) provide a first bias current to the first amplifier or (2) provide a second bias current to the second amplifier, wherein the second bias current is less than the first bias current.

Devices and methods for improving reliability of scalable periphery amplifiers is described. Amplifier segments of the scalable periphery architecture can be rotated to distribute wear. Further, extra amplifier segments can be implemented on amplifier dies to extend the overall lifetime of amplifiers.

Provided herein are apparatus and methods for protecting radio frequency (RF) amplifiers from overdrive. In certain configurations, an RF amplification system includes a plurality of RF amplification stages including a first amplification stage and a second amplification stage subsequent to the first amplification stage in a signal path. The first amplification stage includes a first stage field-effect transistor (FET), and the second amplification stage includes a second stage FET and a gate-to-drain feedback circuit electrically connected between a gate and a drain of the second stage FET. The RF amplification system further includes an overdrive detection circuit that senses a drain current of the first stage FET to detect when an overdrive condition is present, and that decreases an impedance of the gate-to-drain feedback circuit in response to detection of the overdrive condition such that a gain of the second stage FET is reduced.

An amplifier applicable to an intra-band non-contiguous carrier aggregation (NCCA) band includes a first amplifier circuit and a second amplifier circuit. The NCCA band includes at least a primary component carrier (PCC) channel and a secondary component carrier (SCC) channel not adjacent to each other. The first amplifier circuit receives a first input signal, and generates a first output signal for undergoing down-conversion of one of the PCC channel and the SCC channel. The second amplifier circuit receives at least one second input signal, and generates a second output signal for undergoing down-conversion of another of the PCC channel and the SCC channel. The at least one second input signal received by the second amplifier circuit is provided by the first amplifier circuit according to the first input signal.

Described examples include multistage amplifier circuits having first and second forward circuits, a comparator or sensor circuit coupled to sense a signal in the second forward circuit to identify nonlinear operation or slewing conditions in the multistage amplifier circuit, and one or more sample hold circuits operative according to a sensor circuit output signal to selectively maintain the amplitude of an amplifier input signal in the second forward circuit and/or in a feedback circuit in response to the sensor circuit output signal indicating nonlinear operation or slewing conditions in the multistage amplifier circuit. Certain examples further include a clamping circuit operative to selectively maintain a voltage at a terminal of a Miller compensation capacitance responsive to the comparator output signal indicating nonlinear operation or slewing conditions.

A method and apparatus is disclosed to couple a transmission amplifier and a reception amplifier to a shared medium. An output of the transmission amplifier is directly coupled to an input of the reception amplifier to form a common connection. The transmission amplifier and the reception amplifier may receive a first amplifier bias via the common connection. In response to the first amplifier bias, the transmission amplifier provides a first communication signal to the shared medium and the reception amplifier does not provide a second communication signal from the shared medium. Alternatively, the transmission amplifier and the reception may receive a second amplifier bias via the common connection. In response to the second amplifier bias, the reception amplifier provides the second communication signal from the shared medium and the transmission amplifier does not provide the first communication signal to the shared medium.

Provided herein are apparatus and methods for overdrive protection of radio frequency (RF) amplifiers. In certain configurations, an RF amplifier includes a plurality of amplification stages and an overdrive detection circuit. The overdrive detection circuit determines whether or not the RF amplifier is in an overdrive condition based on a current of an input amplification stage. Additionally, when the overdrive detection circuit detects an overdrive condition, the overdrive detection circuit controls an impedance of one or more feedback circuits of one or more amplification stages subsequent to the input amplification stage in a signal path of the RF amplifier to reduce the RF amplifier's gain. The overdrive protection schemes herein can be used to limit large current and voltage swing conditions manifesting within amplification transistors of the RF amplifier.

Power amplifier having a common input and a plurality of outputs. In some embodiments, a power amplifier can include a plurality of signal paths having a common input node. Each signal path can include a dedicated amplifier stage, and be configured to be capable of amplifying a radio-frequency (RF) signal received at the common input node. The power amplifier can further include a bias selector configured to provide a bias signal to the dedicated amplifier stage of a selected one of the plurality of signal paths to thereby allow amplification of the RF signal through the selected signal path. Such a power amplifier can be implemented in products such as a die, a module, and a wireless device.