A radio-frequency device comprises a first radio-frequency signal node, a second radio-frequency signal node, a first power cell path coupled between the first radio-frequency signal node and a ground reference node, the first power cell path including a first transistor having an input terminal coupled to the second radio-frequency signal node, and a second power cell path coupled in parallel with the first power cell path between the first radio-frequency signal node and the ground reference node, the second power cell path including a second transistor having an input terminal coupled to the second radio-frequency signal node and an output terminal that is electrically isolated from an output terminal of the first transistor.

In some embodiments, a filtering technique can include a pre-amplifier filter configured to filter a signal, and an amplifier assembly configured to amplify the filtered signal. The filtering technique can further include a filter circuit configured to provide selective filtering of the amplified signal based at least in part on a rejection level of the pre-amplifier filter and a gain of the amplifier assembly.

Apparatus and methods for low noise amplifiers (LNAs) are provided herein. In certain configurations, an LNA includes a mode control circuit that operates the LNA in one of a plurality of modes including a gain mode and a bypass mode, a gain circuit electrically connected between an input terminal and an output terminal and operable to amplify a radio frequency signal received from the input terminal in the gain mode, and a bypass circuit electrically connected between the input terminal and the output terminal and operable to bypass the gain circuit in the bypass mode. The bypass circuit includes a balun that provides a first amount of compensation for a difference in phase delay between the bypass circuit and the gain circuit, and the LNA further includes a phase compensation circuit operable to provide a second amount of compensation for the difference in phase delay.

Apparatus and methods for reducing inductor ringing of a voltage converter are provided. In certain configurations, a voltage converter includes an inductor connected between a first node and a second node, a plurality of switches, and a bypass circuit having an activated state and a deactivated state. The switches includes a first switch connected between a battery voltage and the first node, a second switch connected between the first node and a ground voltage, a third switch connected between the second node and the ground voltage, and a fourth switch connected between the second node and the output. The bypass circuit includes a first pair of transistors connected between the first node and the second node and configured to turn on to bypass the inductor in the activated state and to turn off in the deactivated state.

An apparatus, comprising an input transformer; a first differential transistor pair configured to receive a first back gate bias voltage; a second differential transistor pair configured to receive a second back gate bias voltage; a cross-coupled neutralization cap comprising PMOS or NMOS transistors and configured to receive a third back gate bias voltage; and an output transformer. A method of fixing at least one back gate bias voltage to impart a desired capacitance to the transistors of at least one of the first differential transistor pair, the second differential transistor pair, or the neutralization cap. The apparatus and method may provide a power amplifier having improved linearity and efficiency.

A scalable periphery tunable matching power amplifier is presented. Varying power levels can be accommodated by selectively activating or deactivating unit cells of which the scalable periphery tunable matching power amplifier is comprised. Tunable matching allows individual unit cells to see a constant output impedance, reducing need for transforming a low impedance up to a system impedance and attendant power loss. The scalable periphery tunable matching power amplifier can also be tuned for different operating conditions such as different frequencies of operation or different modes.

An envelope tracking (ET) power management circuit is provided. The ET power management circuit includes an amplifier circuit(s) configured to output a radio frequency (RF) signal at a defined power level corresponding to a direct current, an alternating current, and an ET modulated voltage received by the amplifier circuit(s). The ET power management circuit can operate in a high-power ET mode when the defined power level exceeds a defined power level threshold and the RF signal is modulated to include no more than a defined number of resource blocks. The ET power management includes two ET tracker circuitries each generating a respective ET modulated voltage and two charge pump circuitries each generating a respective current. In the high-power ET mode, both charge pump circuitries are activated to each provide a reduced current to the amplifier circuit, thus helping to reduce a footprint and cost of the ET power management circuit.

A signal processing chain, such as an audio chain, produces an analog output signal from a digital input signal. The signal processing chain is operated by generating a first flag signal for the analog output signal and one or more second flag signals for the digital input signal. Each flag signal assumes a first level or a second level and is set to the first level when a signal from which the flag is generated has a value within an amplitude window. An amount the first flag signal for the analog output signal and the second flag signal for the digital input signal match each other may be calculated for issuing an alert flag which indicates an impaired operation of the signal processing chain.

In a general aspect, a system can include a fully differential amplifier circuit that includes a first amplifier, and first and second feedback paths. The first feedback path can provide a feedback path from a positive output of the first amplifier to a negative input of the first amplifier. The second feedback path can provide a feedback path from a negative output of the first amplifier to a positive input of the first amplifier. The system can include a chopper clock circuit configured to output a variable duty cycle chopper clock signal. The system can include a common mode loop circuit including a second amplifier and chopper switches. The common mode loop circuit can be configured as a local feedback loop for the first amplifier. The chopper switches can be configured to receive the chopper clock signal and control current flow into the positive and negative inputs.

A power amplifier module includes a combining circuit including a combiner. The combining circuit further includes a first inductor connected in series between an output terminal of a first amplifier and the combiner, a second inductor connected in series between an output terminal of a second amplifier and the combiner, and a second capacitor having an end connected to the combiner and another end grounded. A phase of a third signal from the output terminal of the first amplifier to the second amplifier through the combiner is delayed by about 45 degrees in the first inductor and the second capacitor, and is delayed by about 45 degrees in the second inductor and the second capacitor. A phase of the third signal from the output terminal of the first amplifier to the second amplifier through the first capacitor is advanced by about 90 degrees.