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.

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.

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.

In a portable radio transceiver, a power amplifier system includes a saturation detector that detects power amplifier saturation in response to duty cycle of the amplifier transistor collector voltage waveform. The saturation detection output signal can be used by a power control circuit to back off or reduce the amplification level of the power amplifier to avoid power amplifier control loop saturation.

Apparatus and methods for biasing a power amplifier are disclosed. In one embodiment, a method of biasing a power amplifier includes shaping an enable signal using a time-dependent signal generator to generate a control current, amplifying the control current using a current amplifier to generate a correction current, and generating a bias current for a power amplifier using a primary biasing circuit. The primary biasing circuit is configured to use the correction current to correct for a variation in gain of the power amplifier when the power amplifier is enabled.

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.

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.

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 first transconductance cell having a differential input voltage V1 and a forced output current I1, has a bias set by a feedback loop. A second transconductance cell having a differential input voltage V2 and using the same biasing as the first cell has analytically identical transconductance. The second transconductance cell produces an output current I2 dependent on the product of the output current I1 of the first transconductance cell and the quotient of the second differential input voltage V2, and the first differential input voltage V1. The adaptive transconductance cells can be used to generate mathematic functions such as multiplication and division.

Provided are an audio amplification circuit, a board, and an electronic device. The circuit includes: a boost circuit and an audio amplifier, where the audio amplifier includes a pre-module and a post-module; an input end of the boost circuit is connected to a power supply, an output end of the boost circuit is connected to an input end of the pre-module, and an input end of the post-module is connected to the power supply; the boost circuit is configured to boost a first voltage signal when a voltage value of the received first voltage signal of the power supply is less than a first preset voltage value to obtain a second voltage signal whose voltage value is a second preset voltage value, and send the second voltage signal to the input end of the pre-module, where the second preset voltage value is not less than the first preset voltage value.