One aspect of the present disclosure relates to a method for operating an amplifier, the amplifier including a variable resistor coupled between a source of a first input transistor and a source of a second input transistors, and a variable capacitor coupled between the source of the first input transistor and the source of the second input transistor. The method includes adjusting a resistance of the variable resistor to adjust a low-frequency gain of the amplifier, and adjusting a capacitance of the variable capacitor in an opposite direction as the adjustment to the resistance of the variable resistor.

A method may include receiving information indicative of an amplitude of an audio output signal, receiving information indicative of a predicted voltage of a power supply of a signal path having an audio input for receiving an audio input signal and an audio output for generating the audio output signal based on the audio input signal, predicting from the information indicative of the amplitude of the audio output signal and the information indicative of the predicted voltage of the power supply whether the audio output signal will exceed an available supply voltage generated by the power supply, and responsive to determining the audio output signal will exceed the available supply voltage generated by the power supply, attenuating the audio input signal or a derivative thereof to reduce the amplitude of the audio output signal such that the audio output signal does not exceed the available supply voltage of the power supply.

The embodiments described herein include amplifiers that are typically used in radio frequency (RF) applications. The amplifiers described herein use a buffer that is implemented inside the device package. Specifically, the amplifiers can be implemented with a gate bias modulation buffer inside the device package, where the gate bias modulation buffer is configured to provide a modulated bias signal to a transistor gate of the amplifier.

A differential amplifier generates an output voltage waveform exhibiting a slew rate over a rise time. The amplifier is powered from a dc voltage input and includes a set of differential pairs having a bias current flowing therethrough and a Miller compensation capacitance. A comparator functions to compare a voltage at the dc voltage input against a reference voltage in order to detect when the voltage drops below the reference voltage. A gain stage controls the gain of the differential amplifier and a bias current control circuit controls the bias current of the differential amplifier. In response to the detection by the comparator of the voltage dropping below the reference voltage, the gain stage and the bias current control circuit decrease the gain of the amplifier and jointly decrease the bias current in order to maintain a value of the rise time.

In accordance with embodiments of the present disclosure, a method may include receiving a digital input signal at a first integrated circuit from a second integrated circuit, receiving a supply voltage at the first integrated circuit from the second integrated circuit, generating an analog output signal from the digital input signal, predicting a distortion of the analog output signal based on the digital input signal and the supply voltage, and controlling a gain applied to at least one of the digital input signal and the analog output signal based on the predicting.

Use of a closed loop APC may involve a problem of cost and power consumption due to increased circuit scale.

The semiconductor device includes a power amplifier that amplifies an output from a transmission circuit and a regulator that supplies power to the power amplifier. The regulator includes an operational amplifier comprising a loop gain control circuit and a loop gain control voltage generation circuit that supplies control voltage to the loop gain control circuit. The loop gain control voltage generation circuit minimizes a loop gain of the operational amplifier when starting up the regulator.

One aspect of the present disclosure relates to a method for operating an amplifier, the amplifier including a variable resistor coupled between a source of a first input transistor and a source of a second input transistors, and a variable capacitor coupled between the source of the first input transistor and the source of the second input transistor. The method includes adjusting a resistance of the variable resistor to adjust a low-frequency gain of the amplifier, and adjusting a capacitance of the variable capacitor in an opposite direction as the adjustment to the resistance of the variable resistor.

In a power amplifier module for performing slope control of a transmitting signal, a gain variation due to a variation in battery voltage is suppressed while suppressing an increase in circuit size. The power amplifier module includes: a first regulator for outputting a first voltage corresponding to a control voltage for controlling a signal level; a second regulator for outputting a second voltage that rises as a battery voltage drops; a first amplifier supplied with the first voltage as a power-supply voltage to amplify an input signal and output an amplified signal; and a second amplifier for amplifying the amplified signal, wherein the second amplifier includes a first amplification unit supplied with the second voltage as the power-supply voltage to amplify the amplified signal, and a second amplification unit supplied with the battery voltage as the power-supply voltage to amplify the amplified signal.

Apparatus and methods for biasing of power amplifiers are disclosed. In one embodiment, a mobile device includes a transceiver that generates a radio frequency signal and a power amplifier enable signal, a power amplifier that provides amplification to the radio frequency signal and that is biased by a bias signal, and a bias circuit that receives the power amplifier enable signal and generates the bias signal. The bias circuit includes a gain correction circuit that generates a correction current in response to activation of the power amplifier enable signal, and a primary biasing circuit that generates the bias signal based on the correction current and the power amplifier enable signal.

A load-modulated balanced amplifier (LMBA) based on a variable cross-coupled pair (XCP) is provided. The LMBA includes an adaptive bias (ADB) circuit, a first balance terminal amplifier module, a second balance terminal amplifier module, a control terminal amplifier module, a first driver amplifier module, a second driver amplifier module, a third driver amplifier module, a variable XCP, a resistor R5, a resistor R6, a 90-degree differential coupler Q1, a 90-degree differential coupler Q2, and a 90-degree differential coupler Q3.