An electronic device may include wireless circuitry with a processor, a transceiver, an antenna, and a front-end module coupled between the transceiver and the antenna. The front-end module may include one or more radio-frequency amplifiers for amplifying a radio-frequency signal. The radio-frequency amplifier may include input transistors cross-coupled with capacitance neutralization transistors and/or coupled to cascode transistors. One or more n-type gain adjustment transistors may be coupled to source terminals of the capacitance neutralization transistors. One or more p-type gain adjustment transistors may be coupled to source terminals of the cascode transistors. One or more processors in the electronic device can selectively activate one or more of the gain adjustment transistors to reduce the gain of the radio-frequency amplifier without degrading noise performance and without altering the in-band frequency response of the radio-frequency amplifier.

Envelope tracking power amplifiers with advanced gain shaping are provided. In certain implementations, a power amplifier system includes a power amplifier that amplifies a radio frequency (RF) signal and an envelope tracker that controls a voltage level of a supply voltage of the power amplifier based on an envelope of the RF signal. The power amplifier system further includes a gain shaping circuit that generates a gain shaping current that changes with the voltage level of the supply voltage from the envelope tracker. For example, the gain shaping circuit can include an analog look-up table (LUT) mapping a particular voltage level of the supply voltage to a particular current level of gain shaping current. Additionally, the gain shaping circuit biases the power amplifier based on the gain shaping current.

A method for calibrating an isolator product includes receiving a calibration signal on a differential pair of nodes of a receiver signal path of a first integrated circuit die of the isolator product. The method includes generating a diagnostic signal having a level corresponding to an average amplitude of the calibration signal on the differential pair of nodes. The method includes configuring a programmable receiver signal path based on the diagnostic signal. Generating the diagnostic signal may include providing an analog signal based on a full-wave rectified version of the calibration signal on the differential pair of nodes. Generating the diagnostic signal may include converting the analog signal to a digital signal.

An apparatus for amplifying an audio source includes a speaker and a chip. The chip includes a processor configured to generate a signal and an amplifier element configured to amplify the signal into an amplified signal. The chip further includes a current monitor configured to monitor the current of the amplified signal prior to the amplified signal being output from the chip to the speaker and a voltage monitor configured to monitor the voltage of the amplified signal prior to the amplified signal being output from the chip to the speaker. The processor of the chip is configured to control a power of the amplified signal output from the chip to the speaker based at least on the current and the voltage.

A signal processing circuit includes a signal path for outputting a first signal included in an input signal from a first output terminal to another signal processor; branch paths one of which extends from a top position located at a position on the signal path and the others which extend from associated branch positions that divide the signal path starting from the top position to the first output terminal into segments in each of which a first amount of delay obtained by equally dividing an amount of delay caused by the signal path and that is added to the first signal; a switch connected to each of the branch paths and switches whether to allow a second signal other than the first signal included in the input signal to pass through the connected branch paths; a variable gain amplifier connected to each of the switches and amplifies the second signal.

A method and apparatus for measuring a biopotential signal together with impedance changes uses electrodes on a subject’s skin and for compensating for such impedances to increase accuracy and usability of such devices for short-and long-term monitoring of biosignals. The apparatus can include a first terminal for connection to a first electrode, a second terminal for connection to a second electrode, a first circuitry configured for measuring the biopotential signal from the first and the second terminal, a third terminal for connection to the reference skin electrode, a first variable controlled resistance load connected to the first terminal, and a second variable controlled resistance load connected to the second terminal.

The invention is an apparatus used to send sound exterior to the vehicle to a location on the interior of a vehicle which corresponds with the sound’s external location. The apparatus adjusts for gain by frequency and shifts frequencies of the audio signals received exterior to the vehicle to generate a modified audio signal. The adjustments include compensation for hearing loss, compensation for audio in the interior of the vehicle, and attenuation adjustments for unwanted exterior noise. The modified audio signal is generated by filtering unwanted audio from the exterior audio, adjusting for gain by frequency and shifting/compressing frequencies according to hearing deficiencies, and adjusting for gain by frequency according to audio in the interior of the vehicle. The modified audio signal may be limited to a maximum gain and then amplified in the interior of the vehicle.

A voltage detection circuit includes a differential amplification circuit and a microcontroller unit (MCU). The MCU detects a differential voltage output from operational amplifiers of the differential amplification circuit, and calculates an internal resistance value of a battery cell based on the detected differential voltage. At this time, the MCU controls an amplification factor adjustment circuit of the differential amplification circuit based on a maximum voltage representing the highest voltage detectable by the MCU and the differential voltage output from the differential amplification circuit so as to set the amplification factor of the operational amplifiers.

A peak detector for a power amplifier is provided that includes a threshold voltage detector configured to pulse a detection current in response to an amplified output signal from the amplifier exceeding a peak threshold. A plurality of such peak detectors may be integrated with a corresponding plurality of power amplifiers in a transmitter. Should any peak detector assert an alarm signal or more than a threshold number of alarm signals during a given period, a controller reduces a gain for the plurality of power amplifiers.

Methods, systems, and devices for delay adjustment circuits are described. Amplifiers (e.g., differential amplifiers) may act like variable capacitors (e.g., due to the Miller-effect) to control delays of signals between buffer (e.g., re-driver) stages. The gains of the amplifiers may be adjusted by adjusting the currents through the amplifiers, which may change the apparent capacitances seen by the signal line (due to the Miller-effect). The capacitance of each amplifier may be the intrinsic capacitance of input transistors that make up the amplifier, or may be a discrete capacitor. In some examples, two differential stages may be inserted on a four-phase clocking system (e.g., one on 0 and 180 phases, the other on 90 and 270 phases), and may be controlled differentially to control phase-to-phase delay.