A control device includes: a differential amplification circuit that amplifies a difference with respect to an input signal; and a clipping circuit that is connected to an output side of the differential amplification circuit and clips an input voltage. The differential amplification circuit includes a plurality of switching elements formed of a GaN semiconductor, and the clipping circuit includes a switching element formed of the GaN semiconductor.

A source follower with an input node and an output node includes a first transistor, a second transistor, and a DC (Direct Current) tracking circuit. The first transistor has a control terminal, a first terminal coupled to a first node, and a second terminal coupled to a second node. The second transistor has a control terminal, a first terminal coupled to a ground voltage, and a second terminal coupled to the first node. The DC tracking circuit sets the second DC voltage at the second node to a specific level. The specific level is determined according to the first DC voltage at the first node. The output node of the source follower is coupled to the first node.

An apparatus for controlling the gain and phase of an input signal input to a power amplifier comprises a gain control loop configured to control the gain of the input signal based on power levels of the input signal and an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, and a phase control loop configured to obtain an error signal related to a phase difference between a first signal derived from the input and a second signal derived from the amplified signal, and control the phase based on the error signal, to obtain a predetermined phase of the amplified signal. The phase control loop delays the first signal such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. The apparatus may be included in a satellite.

A close-down pop reduction system and a method for close-down pop reduction in an audio amplifier assembly are disclosed. The switching power conversion system comprises a forward path having a compensator and a switching power stage and a signal path from an output of a comparator in the switching power stage to a sequence control unit. The signal path includes a close-down timing circuit configured to provide a timing signal. The sequence control unit is configured to eliminate the input signal, increase the switch frequency of the close-down pop reduction system and disable the switching power stage at a moment in time within a PWM pulse of the switching power stage. Hereby, it is e.g. possible to minimize the audible pop during close-down of audio amplifier assemblies.

A method and apparatus for high-speed clipping and recovery in an amplifier circuit is disclosed. In one embodiment, a circuit includes an amplifier configured to amplify an incoming signal. The amplifier includes inverting and non-inverting inputs, and is configured to provide a differential output. An output limiting circuit is coupled across the differential output, and is configured to limit an amplitude of an output signal provided on the differential output responsive to an input signal exceeding a first amplitude threshold. An input limiting circuit is coupled between the inverting input and the non-inverting input of the amplifier. Responsive to the input signal exceeding a second amplitude threshold (greater than the first), the input limiting circuit is configured to limit the amplitude of the output signal.

A new method for amplifying signals having higher bandwidth, lower T.H.D, higher efficiency, smaller circuit size and lower costs in design, has been developed. A clipped signal is amplified to smaller pieces and each smaller part is amplified. Adding clipped amplified signals to each other, the main amplified signal is generated.

Systems and methods are provided for dynamically biasing power amplifiers. In particular, dynamic biasing of a power amplifier may be controlled, with the controlling comprising receiving an input signal that is to be amplified; processing the input signal; generating based on said processing of the input signal input signal, a plurality of control signals comprising at least one biasing control signal; and applying the plurality of control signals to one or more control elements that are used in driving and/or control of the power amplifier. The one or more control elements may comprise at least one biasing component that adjusts biasing applied to power amplifier.

A distortion compensation device includes a distortion compensation unit, a feedback coefficient calculating unit, a clip processing unit, and an updating unit. The distortion compensation unit generates a distortion compensation signal from a transmission signal by using a distortion compensation coefficient and inputs the generated distortion compensation signal to a power amplifier. The feedback coefficient calculating unit calculates a feedback coefficient based on an output signal from the power amplifier. The clip processing unit outputs the feedback coefficient when absolute value of the feedback coefficient is less than a threshold. Furthermore, the clip processing unit outputs a feedback coefficient of which absolute value is less than the threshold when the absolute value of the feedback coefficient is greater than the threshold. The updating unit updates the distortion compensation coefficient by using an error between the transmission signal and the output signal, a predetermined step coefficient, and the feedback coefficient.

A power conversion system comprising an amplifier input for receiving an analogue input signal and an amplifier output for providing a switching output signal is disclosed. The system is applicable for use in high definition switching audio amplification. The power conversion system further comprises a clipper for clipping the analogue input signal having a predefined range limited by a clipping level, a pulse modulator and a switching power stage. The system further has a feedback path to the clipper including a duty cycle measuring unit and a clip level filter which generates a clip level signal and where the clipping level of the clipper is controlled by the clip level signal. Hereby it is e.g. possible to clip an analogue input signal with good precision and reliability in a switching power conversion system.

A musical instrument preamplifier includes a n-type JFET and a pnp current mirror connected to the drain side of the JFET. The pnp current mirror includes two pnp transistors. The current mirror is configured to control the current to independently set the operating point of the JFET and the output. An npn transistor is connected to one of the pnp transistors of the current mirror to form an inverted Sziklai pair. An auto-bias network is connected between the npn and pnp transistors that form the Sziklai pair.