Circuits and methods related to switchless carrier aggregation in radio-frequency receivers. In some embodiments, a carrier aggregation (CA) circuit can include a first filter configured to allow operation in a first frequency band, and a second filter configured to allow operation in a second frequency band. The CA circuit can further include a first signal path implemented between the first filter and an output node, with the first signal path including a plurality of amplification stages configured to amplify a first radio-frequency (RF) signal. The first signal path can be substantially free of switches. The CA circuit can further include a second signal path implemented between the second filter and the output node, with the second signal path including a plurality of amplification stages configured to amplify a second RF signal. The second signal path can be substantially free of switches.

Circuits and methods related to switchless carrier aggregation in radio-frequency receivers. In some embodiments, a carrier aggregation (CA) circuit can include a first filter configured to allow operation in a first frequency band, and a second filter configured to allow operation in a second frequency band. The CA circuit can further include a first signal path implemented between the first filter and an output node, with the first signal path including a plurality of amplification stages configured to amplify a first radio-frequency (RF) signal. The first signal path can be substantially free of switches. The CA circuit can further include a second signal path implemented between the second filter and the output node, with the second signal path including a plurality of amplification stages configured to amplify a second RF signal. The second signal path can be substantially free of switches.

Diversity receiver front end system with post-amplifier filters. A receiving system can include a controller configured to selectively activate one or more of a plurality of paths between an input of a first multiplexer and an output of a second multiplexer. The receiving system can further include a plurality of amplifiers. Each one of the plurality of amplifiers can be disposed along a corresponding one of the plurality of paths and can be configured to amplify a signal received at the amplifier. The receiving system can include a first plurality of bandpass filters. Each one of the first plurality of bandpass filters can be disposed along a corresponding one of the plurality of paths at an output of a corresponding one of the plurality of amplifiers and can be configured to filter a signal received at the bandpass filter to a respective frequency band.

Diversity receiver front end system with post-amplifier filters. A receiving system can include a controller configured to selectively activate one or more of a plurality of paths between an input of a first multiplexer and an output of a second multiplexer. The receiving system can further include a plurality of amplifiers. Each one of the plurality of amplifiers can be disposed along a corresponding one of the plurality of paths and can be configured to amplify a signal received at the amplifier. The receiving system can include a first plurality of bandpass filters. Each one of the first plurality of bandpass filters can be disposed along a corresponding one of the plurality of paths at an output of a corresponding one of the plurality of amplifiers and can be configured to filter a signal received at the bandpass filter to a respective frequency band.

Systems, devices and methods related to multi-band power amplifier. In some embodiments, a power amplifier module includes a power amplifier having an output stage and configured to receive a signal. The power amplifier module also includes a first programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier. The first programmable harmonic termination circuit includes a first plurality of capacitors and a first plurality of switches, with at least one of the first plurality of capacitors being in electrical communication with at least one of the first plurality of switches. The power amplifier module further includes a controller configured to modify a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

Systems, devices and methods related to multi-band power amplifier. In some embodiments, a power amplifier module includes a power amplifier having an output stage and configured to receive a signal. The power amplifier module also includes a first programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier. The first programmable harmonic termination circuit includes a first plurality of capacitors and a first plurality of switches, with at least one of the first plurality of capacitors being in electrical communication with at least one of the first plurality of switches. The power amplifier module further includes a controller configured to modify a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

A bias circuit for power amplifiers is disclosed. A power amplifier bias circuit can include an emitter follower device and an emitter follower mirror device coupled to form a mirror configuration. The emitter follower device can be configured to provide a bias signal for a power amplifier at an output port. The power amplifier bias circuit can include a reference device configured to mirror an amplifying transistor of an amplifying device of the power amplifier. The emitter follower mirror device can be configured to provide a mirror bias signal to the reference device. A node between the emitter follower device and the emitter follower mirror device can have a voltage of approximately twice a base-emitter voltage (2 Vbe) of the amplifying transistor.

A bias circuit for power amplifiers is disclosed. A power amplifier bias circuit can include an emitter follower device and an emitter follower mirror device coupled to form a mirror configuration. The emitter follower device can be configured to provide a bias signal for a power amplifier at an output port. The power amplifier bias circuit can include a reference device configured to mirror an amplifying transistor of an amplifying device of the power amplifier. The emitter follower mirror device can be configured to provide a mirror bias signal to the reference device. A node between the emitter follower device and the emitter follower mirror device can have a voltage of approximately twice a base-emitter voltage (2 Vbe) of the amplifying transistor.

Systems and methods for controlling a power amplifier includes combining a digital modulated data signal with a digital bias signal to generate a combined digital signal, the digital bias signal generated based on an envelope for the modulated data signal; converting, by a digital-to-analog converter, the combined digital signal into a combined analog signal, the combined analog signal comprising an analog modulated data signal and an analog envelope bias signal; and separating the analog modulated data signal and the analog bias signal onto separate signal paths, wherein the converting is performed using a single digital-to-analog converter.

Systems and methods for controlling a power amplifier includes combining a digital modulated data signal with a digital bias signal to generate a combined digital signal, the digital bias signal generated based on an envelope for the modulated data signal; converting, by a digital-to-analog converter, the combined digital signal into a combined analog signal, the combined analog signal comprising an analog modulated data signal and an analog envelope bias signal; and separating the analog modulated data signal and the analog bias signal onto separate signal paths, wherein the converting is performed using a single digital-to-analog converter.