An apparatus includes an amplifier circuit and a protection circuit. The amplifier circuit may be configured to generate an output signal by amplifying an input signal received at an input port. The input signal may be a radio-frequency signal. The protection circuit may be configured to (i) generate a detection signal by detecting when a level of the input signal exceeds a corresponding threshold, where the level is a power level, a voltage level or both, (ii) route the input signal away from the input port of the amplifier circuit and disable the amplifier circuit both in response to the detection signal being continuously active at least a first time duration and (iii) route the input signal to the input port of the amplifier circuit and enable the amplifier circuit both in response to the detection signal being continuously inactive at least a second time duration.

The present document describes a digital power amplifier configured to provide an amplified output signal at an output port based on an input signal. The power amplifier comprises a drive unit configured to generate a high side drive signal comprising a sequence of pulses for controlling the high side switch and a low side drive signal comprising a sequence of pulses for controlling the low side switch, respectively. The drive signals are generated such that the pulses of the high side drive signal are non-overlapping with regards to the pulses of the low side drive signal, and such that the sequence of pulses of the high side drive signal and the sequence of pulses of the low side drive signal have a reduced fraction of energy from higher order harmonics compared to a sequence of rectangular shaped pulses.

A power tube driver of a class-D audio amplifier includes high-side and low-side fixed charge/discharge gate driving circuits, high-side and low-side power tubes, a dead time generation circuit based on gate voltage detection, high-side and low-side gate charge/discharge accelerating circuits, and high-side and low-side gate voltage detection circuits. The class-D audio amplifier with the features of low radiation interference, and high efficiency, linearity and robustness can be balanced easily.

A power tube driver of a class-D audio amplifier includes high-side and low-side fixed charge/discharge gate driving circuits, high-side and low-side power tubes, a dead time generation circuit based on gate voltage detection, high-side and low-side gate charge/discharge accelerating circuits, and high-side and low-side gate voltage detection circuits. The class-D audio amplifier with the features of low radiation interference, and high efficiency, linearity and robustness can be balanced easily.

A single-ended Class-A amplifier includes an amplification component (e.g., a vacuum tube) having at least an output terminal, a reference terminal and a control terminal. The control terminal receives a time-varying input signal. The amplification component responds to the time-varying input signal to vary an output voltage on the output terminal and to vary a current flowing between the output terminal and the reference terminal. A load is AC-coupled to the output terminal. A steered current source has a voltage input coupled to the output terminal and has a steered current output coupled to the output terminal. The steered current source is configured to increase the steered current to provide current to the load when the output voltage on the output terminal of the amplification component increases and to decrease the steered current when the output voltage on the output terminal of the amplification component decreases.

A single-ended Class-A amplifier includes an amplification component (e.g., a vacuum tube) having at least an output terminal, a reference terminal and a control terminal. The control terminal receives a time-varying input signal. The amplification component responds to the time-varying input signal to vary an output voltage on the output terminal and to vary a current flowing between the output terminal and the reference terminal. A load is AC-coupled to the output terminal. A steered current source has a voltage input coupled to the output terminal and has a steered current output coupled to the output terminal. The steered current source is configured to increase the steered current to provide current to the load when the output voltage on the output terminal of the amplification component increases and to decrease the steered current when the output voltage on the output terminal of the amplification component decreases.

The present invention provides a vacuum tube audio amplifier which includes an audio pre-amplifying portion and an audio output transforming portion. The audio pre-amplifying portion includes an equalizer for enhanced sound quality and amplifies an audio signal, which is subsequently transmitted to the audio output transforming portion. Furthermore, the audio output transforming portion includes an audio output transformer which includes a plurality of stacked E-shaped silicon steel sheets and a plurality of stacked I-shaped silicon steel sheets, wherein the stacked E-shaped silicon steel sheets and the stacked I-shaped silicon steel sheets have a same height which is smaller than or equal to 48 mm.

The present invention provides a vacuum tube audio amplifier which includes an audio pre-amplifying portion and an audio output transforming portion. The audio pre-amplifying portion includes an equalizer for enhanced sound quality and amplifies an audio signal, which is subsequently transmitted to the audio output transforming portion. Furthermore, the audio output transforming portion includes an audio output transformer which includes a plurality of stacked E-shaped silicon steel sheets and a plurality of stacked I-shaped silicon steel sheets, wherein the stacked E-shaped silicon steel sheets and the stacked I-shaped silicon steel sheets have a same height which is smaller than or equal to 48 mm.

The present invention provides a vacuum tube audio amplifier which includes an audio pre-amplifying portion and an audio output transforming portion. The audio pre-amplifying portion includes an equalizer for enhanced sound quality and amplifies an audio signal, which is subsequently transmitted to the audio output transforming portion. Furthermore, the audio output transforming portion includes an audio output transformer which includes a plurality of stacked E-shaped silicon steel sheets and a plurality of stacked I-shaped silicon steel sheets, wherein the stacked E-shaped silicon steel sheets and the stacked I-shaped silicon steel sheets have a same height which is smaller than or equal to 48 mm.

The present invention provides a vacuum tube audio amplifier which includes an audio pre-amplifying portion and an audio output transforming portion. The audio pre-amplifying portion includes an equalizer for enhanced sound quality and amplifies an audio signal, which is subsequently transmitted to the audio output transforming portion. Furthermore, the audio output transforming portion includes an audio output transformer which includes a plurality of stacked E-shaped silicon steel sheets and a plurality of stacked I-shaped silicon steel sheets, wherein the stacked E-shaped silicon steel sheets and the stacked I-shaped silicon steel sheets have a same height which is smaller than or equal to 48 mm.