Multi-level envelope tracking systems with adjusted voltage steps are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, and a modulator output filter coupled between an output of the MLS modulator and the power amplifier supply voltage. The envelope tracking system further includes a switching point adaptation circuit configured to control the voltage level of the regulated voltages outputted by the MLS DC-to-DC converter based on a power level of the RF signal.

A radio frequency front end circuit for a multimode transceiver has a first operating mode transmit input port, a second operating mode transmit input/receive output port, and a hybrid first and second operating mode receive output port. A first switch network has one or more switch elements together selectively connecting the first operating mode transmit input port, the second operating mode transmit input/receive output port, and the hybrid first and second operating mode receive output port to a coexistence filter first port. A second switch network has one or more switch elements that together selectively connect a coexistence filter second port to an antenna port.

Systems and methods are provided for amplifying multiple input signals to generate multiple output signals. An example system includes a first channel, a second channel, and a third channel. The first channel is configured to receive one or more first input signals, process information associated with the one or more first input signals and a first ramp signal, and generate one or more first output signals. The second channel is configured to receive one or more second input signals, process information associated with the one or more second input signals and a second ramp signal, and generate one or more second output signals. The first ramp signal corresponds to a first phase. The second ramp signal corresponds to a second phase. The first phase and the second phase are different.

Aspects of this disclosure relate to a surface acoustic wave filter with an integrated temperature sensor. The integrated temperature sensor can be a resistive thermal device configured as a reflective grating for a surface acoustic wave resonator, for example. A radio frequency system can provide over temperature protection by reducing a power level of a radio frequency signal provided to the surface acoustic wave filter responsive to an indication of temperature provided by the integrated temperature sensor satisfying a threshold.

Circuits and devices related to radio-frequency amplifiers. In some embodiments, a radio-frequency amplifier can include a plurality of narrow band power amplifiers. Each narrow band power amplifier can be configured to operate with a high voltage in an average power tracking mode and be capable of being coupled to an output filter associated with a respective individual frequency band. Each narrow band power amplifier can be sized smaller than a wide band power amplifier configured to operate with more than one of the frequency bands associated with the plurality of narrow band power amplifiers.

Bulk acoustic wave resonators of two or more different filters can be on a common die. The two filters can be included in a multiplexer, such as a duplexer, or implemented as standalone filters. With bulk acoustic wave resonators of two or more filters on the same die, the filters can be implemented in less physical space compared to implementing the same filters of different die. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.

A class-D amplifier with multiple “nested” levels of feedback. The class-D amplifier surrounds an inner feedback loop, which takes the output of a switching amplifier and corrects for errors generated across the switching amplifier, with additional feedback loops that also take the output of the switching amplifier.

A distortion compensation device includes: a first distortion compensation circuit having a first distortion compensation characteristic for compensating for a first distortion occurring in an output of an amplifier, the first distortion compensation circuit being configured to compensate for the first distortion; a second distortion compensation circuit having a second distortion compensation characteristic for compensating for a second distortion occurring in the output of the amplifier, the second distortion compensation circuit being configured to compensate for the second distortion; and an update unit configured to update the second distortion compensation characteristic. The first distortion includes a non-linear distortion and a memory effect distortion, the second distortion is a distortion whose temporal change is quicker than the first distortion, and the update unit updates the second distortion compensation characteristic at a higher frequency than an update frequency of the first distortion compensation characteristic.

A noise detecting circuit including an amplifier circuit, a filtering circuit and a comparing circuit. The amplifier circuit is arranged to amplify an input signal and output an amplified signal, wherein the input signal is received from a circuit to be detected and indicates a noise level of the circuit to be detected. The filtering circuit is coupled to the amplifier circuit and arranged to filter the amplified signal and output a filtered signal. The comparing circuit is coupled to the filtering circuit and arranged to compare the filtered signal to a reference voltage and output an output signal indicating the noise level of the circuit to be detected.

An amplifier is presented with a sample and average common mode feedback resistor. The amplifier circuit includes a feedback capacitor and a feedback resistor in parallel with the feedback capacitor, where the feedback capacitor and the feedback resistor form part of the negative feedback path for the amplifier. Of note, the feedback resistor is comprised of a low pass filter in series with a switched capacitor resistor, such that the low pass filter is electrically coupled to the output of the amplifier circuit and the switched capacitor resistor is electrically coupled to the inverting input of the amplifier circuit. The amplifier circuit further includes a control circuit interfaced with switches of the switched capacitor resistor. The high pass corner of the switched capacitor resistor is preferably lower than corner of the low pass filter.