Apparatus and methods for power amplifier signal limiting are disclosed. In certain embodiments, a power amplifier system includes a power amplifier that amplifies a radio frequency input signal, and a signal limiter operable to limit a signal power of the power amplifier when the radio frequency input signal exceeds a threshold. The signal limiter includes a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency input signal, and a latch configured to lock the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded.

A receiver includes an amplification block supporting carrier aggregation (CA). The amplification block includes a first amplifier circuit configured to receive a radio frequency (RF) input signal at a block node from an outside source, amplify the RF input signal, and output the amplified RF input signal as a first RF output signal. The first amplifier circuit includes a first amplifier configured to receive the RF input signal through a first input node to amplify the RF input signal, and a first feedback circuit coupled between the first input node and a first internal amplification node of the first amplifier to provide feedback to the first amplifier.

The present disclosure facilitates impedance matching between a power amplifier and filters. A radio-frequency circuit includes a power amplifier, a plurality of transmit filters, a switch, a plurality of first matching networks, and a second matching network. The switch switches the plurality of transmit filters to be coupled to the power amplifier. The plurality of first matching networks are coupled between the plurality of transmit filters and the switch. The second matching network is coupled between the power amplifier and the switch. The second matching network includes a transmission line transformer.

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage, and an envelope tracker including a signal bandwidth detection circuit configured to generate a detected bandwidth signal based on processing an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker further includes a switch bank configured to receive a plurality of regulated voltages, a filter configured to filter an output of the switch bank to generate the power amplifier supply voltage, and a mode control circuit configured to control a filtering characteristic of the filter based on the detected bandwidth signal.

A radio-frequency circuit includes a first power amplifier that outputs a first transmission signal and a second power amplifier that outputs a second transmission signal having a frequency different from a frequency of the first transmission signal. In a period in which the first transmission signal the second transmission signal are simultaneously outputted, at least one of the first power amplifier or the second power amplifier reduces transmission power of the at least one of the first power amplifier or the second power amplifier to cause a power component of intermodulation distortion superimposed on a transmission signal output from the first power amplifier and the second power amplifier to be less than or equal to a threshold value.

An integrated circuit can include an amplifier coupled to receive an analog input signal, an anti-aliasing filter (AAF) coupled to an output of the amplifier, a buffer circuit coupled to an output of the AAF, a sigma-delta modulator configured to generate a digital data stream in response to an output of the buffer, and a plurality of chopping circuits nested within one another, including a first pair of chopping circuits having at least the amplifier disposed therebetween and configured to remove offset in the analog input signal, and a second pair of chopping circuit having at least the first pair of chopping circuits disposed therebetween. The amplifier, AAF, sigma-delta modulator, and chopping circuits can be formed with the same integrated circuit substrate. Corresponding methods and systems are also disclosed.

A low-noise amplifier includes a low-noise amplifier stage and a filtering and biasing stage. The low-noise amplifier stage receives an input signal and provides a first output signal in response thereto. The low-noise amplifier stage includes a gain element for proving the first output signal, and at least one lowpass filter circuit in series between a first power supply voltage terminal and the gain element having a conductivity determined by lowpass filtering a signal at a bias terminal, and a filtering and biasing stage having an input for receiving the first output signal, and an output for providing a second output signal, and at least one cascode element having a first current conduction path coupled in series between the bias terminal and the output, and having a predetermined filter characteristic.

An acoustic wave device includes a laminated film on a support substrate and inside a portion of an outer edge of the support substrate in plan view and including a piezoelectric thin film, an IDT electrode on the laminated film, an insulating layer on the support substrate and the laminated film and extending from a region above the support substrate to a region above the laminated film, a connecting electrode on the insulating layer and electrically connected to the IDT electrode, and an external connection terminal electrically connected to the connecting electrode and disposed directly on or above the connecting electrode and outside a region where the laminated film is on the support substrate. A principal surface of the support substrate on the laminated film side includes a recess at an outer edge of the laminated film, and the recess is covered with the insulating layer.

According to various embodiments, an electronic device may include: a communication processor, a radio frequency (RF) integrated circuit (RFIC) configured to receive a signal output from the communication processor and to modulate the signal into an RF signal, a power management circuit, a first power amplifier configured to amplify an RF signal output from the RFIC based on power supplied from the power management circuit, a second power amplifier configured to amplify the RF signal output from the RFIC based on the power supplied from the power management circuit, at least one capacitor connected in parallel to a power supply terminal of the first power amplifier, and at least one switch connected between the power supply terminal and the at least one capacitor, wherein the communication processor is configured to: identify a power amplification mode based a frequency band of the RF signal, and control the at least one switch by outputting a control signal corresponding to the identified power amplification mode.

An analog front-end circuit capable of dynamically adjusting gain includes a programmable gain amplifier (PGA) circuit, a sensor, a calculation circuit, a gain coarse control circuit and a gain fine control circuit. The PGA circuit includes an amplifier, a gain coarse adjustment circuit and a gain fine adjustment circuit. The gain coarse adjustment circuit is controlled by a coarse control signal, and a gain is adjusted in a coarse step according to an initial gain. The gain fine adjustment circuit is controlled by a fine control signal in a data mode, and the gain is adjusted in a fine step. The calculation circuit calculates a primary gain adjustment and a secondary gain adjustment. The gain coarse control circuit generates the coarse control signal according to the primary gain adjustment, and the gain fine control circuit generates the fine control signal according to the secondary gain adjustment.