A transmission circuit includes a power amplifier, a power amplifier forestage circuit and a signal strength adjusting circuit. The power amplifier is configured to amplify an input signal to output an output signal. The power amplifier forestage circuit is configured to output the input signal. The signal strength adjusting circuit includes a conversion circuit, a processing circuit and a storage unit. The conversion circuit is configured to convert the voltage of the output signal into an operation value. The processing circuit is configured to perform an operation according to a target index value stored by the storage unit and the operation value to obtain a differential value. The processing circuit is further configured to adjust the input signal outputted by the power amplifier forestage circuit according to the differential value, so that the power of the output signal is maintained at a target power value.

Differential control circuitry configured to control the operation of a power converter. The control circuitry of this disclosure is configured to receive two differential feedback signals from a fully differential amplifier. The amplifier receives an output voltage (Vout) from the switched mode power supply as well as a reference voltage (Vref). When Vout is less than Vref, the control circuitry may output a pulse width modulation (PWM) control signal to the switched mode power supply with a duty cycle of the PWM control signal based on a relative difference between a positive difference voltage and a negative difference voltage. When Vout is greater than Vref, the control circuitry may output a pulse frequency modulation (PFM) control signal to the switched mode power supply with a switching time of the PFM control signal based on a relative difference between the positive difference voltage and the negative difference voltage.

An RF power detector adapted to detect an RF power of an RF signal, includes, in part, an antenna adapted to receive the RF signal, a narrow-band RF power converter adapted to convert the RF signal to a DC signal, an accelerometer, and a magnetometer. The accelerometer and magnetometer are adapted to determine the orientation and location of the power detector. The power detector optionally includes a gyroscope. The narrow-band RF power converter may be a rectifier tuned to the frequency of the RF signal. The power detector optionally includes an indicator adapted to provide information representative of the amount of the DC power of the DC signal, as well as position and orientation of the power detector. The power detector may be adapted to be inserted into a mobile device so as to provide the information about the amount of DC power, orientation and position to the mobile device.

Techniques are described for using valley detection for supply voltage modulation in power amplifier circuits. Embodiments operate in context of a power amplifier circuit configured to be driven by a supply voltage generated by a supply modulator and to receive an amplitude-modulated (AM) signal at its input. The output of the power amplifier circuit can be fed to a valley detector that can detect a valley level corresponding to the bottom of the envelope of the AM signal. The detected valley level can be fed back to the supply modulator and compared to a constant reference. In response to the comparison, the supply modulator can vary the supply voltage to the power amplifier circuit in a manner that effectively tracking the envelope of the power amplifier circuit's output signal, thereby effectively seeking a flat valley for the output signal's envelope.

Systems and devices configured by an algorithm to prevent or limit a speaker over-excursion are disclosed. The disclosed algorithm is computationally efficient because it exploits a relationship between an audio signal and a speaker's excursion that exists at low-frequencies, below a self-resonance of a speaker. The disclosed algorithm combines the low-frequency excursion protection with a high-frequency, transient excursion protection. The combined approach allows the transient excursion protection to use a shorter delay than otherwise possible. The shorter delay allows for a compressor to apply attenuation to a transient audio signal before a momentum of the speaker, caused by the transient audio signal, grows too large to be controlled.

In an embodiment, a method for determining the phase shift between a first signal and a second signal includes: delivering the first signal to a first input of a 90° hybrid coupler; delivering the second signal to a second input of the 90° hybrid coupler; determining a first piece of information relating to a power of a first output signal delivered to a first output of the 90° hybrid coupler; determining a second piece of information relating to a power of a second output signal delivered to a second output of the coupler; and adjusting the phase of the second signal until obtaining a calibrated phase for which the first piece of information is substantially equal to the second piece of information, wherein the first and second signals have identical frequencies, and wherein the phase shift between the first signal and the second signal is equal to the calibrated phase.

Amplifier architecture that allows low-cost class-D audio amplifiers to be compatible with ultrasonic signals, as well as loads presented by thin-film ultrasonic transducers. The amplifier architecture replaces the traditional capacitor used as an output filter in the class-D amplifier with the natural capacitance of the ultrasonic transducer load, and employs relative impedance magnitudes to create an under-damped low-pass filter that boosts voltage in the ultrasonic frequency band of interest. The amplifier architecture includes a secondary feedback loop to ensure that correct output voltage levels are provided.

A reconfigurable amplifier configured to decrease radio frequency (RF) signal distortion and increase dynamic range is disclosed. The reconfigurable amplifier includes an amplifier having an RF signal input, an RF signal output, and a bias signal input. A distortion detection network has a detector input coupled to the RF signal output and a detector output, wherein the distortion detector network is configured to generate a detection signal that is proportional to distortion at the RF signal output. A bias controller has a detection signal input coupled to the detector output and a bias output coupled to the bias signal input. The bias controller is configured to generate a bias signal that dynamically shifts level at the bias output to reduce the distortion at the RF signal output in response to the detection signal.

A receiving circuit and an optical receiver including the receiving circuit are disclosed. The receiving circuit includes first and second input terminals, a FET, first and second TIA circuits, and a control circuit. The first and second input terminals each receive a current signal. The FET has first and second current terminals respectively connected to the first and second input terminals, and a control terminal. The first and second TIA circuits respectively are connected to the first and second current terminals, and convert the current signals to first and second voltage signals. The control circuit generates a control signal for application to the FET control terminal in accordance with a difference between the first and second voltage signals. The optical receiver includes the receiving circuit and each of first and second photodetectors for respectively supplying first and second current signals to the first and second input terminals of the receiver.

According to one or more embodiments of the disclosure, an electronic device may include a power amplifier, a voltage generator, an antenna, and a communication processor. The CP determines whether an output waveform of the transmission signal which is output through the antenna is a first waveform or a second waveform. If the output waveform is the first waveform, the voltage generator generates a first output voltage for amplifying the first waveform by applying a first direct current (DC) power source of one or more first voltages. If the output waveform is the second waveform, the voltage generator generates a second output voltage for amplifying the second waveform by applying a second DC power source of a second voltage shifted by a designated level with respect to the first voltage, based on a peak power of the first waveform and a peak power of the second waveform.