A method for use with a sound system (called plant in control theory) including a loudspeaker set, the method comprising: obtaining input audio samples and a measured current drawn by the loudspeaker set; generating, for a current time step, using a state-space model of the loudspeaker set, a state vector and a model-based estimated current; generating, based on the state vector, a predicted current for a next time step; generating, for the current time step, a replacement audio sample based on the state vector; generating a feedback signal that contributes to the generation of the state vector for the next time step based on the measured current and a time-aligned model-based estimated current; generating an output audio sample for the current time step, wherein the output audio sample is either the input audio sample for the current time step or the replacement audio sample when the predicted current is higher in magnitude than a threshold.

A clamping circuit that may be used to provide efficient and effective voltage clamping in an RF front end. The clamping circuit comprises two series coupled signal path switches and a bypass switch coupled in parallel with the series coupled signal path switches. A diode is coupled from a point between the series coupled signal path switches to a reference potential. In addition, an output selection switch within an RF front end has integrated voltage clamping to more effectively clamp the output voltage from the RF front end. Additional output clamping circuits can be used at various places along a direct gain signal path, along an attenuated gain path and along a bypass path.

In an embodiment, an amplifier circuit includes a second stage that includes a first switch circuit including first and second terminals, a plurality of resistive elements coupled between the first and second terminals of the first switch circuit, and a plurality of switches configured to control an equivalent resistance between the first and second terminals of the first switch circuit. During play mode, the second stage has a gain between the input of the second stage and the output of the second stage of a first value. During a transition from mute mode to play mode, the amplifier circuit is configured to progressively increase the gain of the second stage from a second value to the first value. During a transition from play mode to mute mode, the amplifier circuit is configured to progressively decrease the gain of the second stage from the first value to the second value.

A current sense amplifier measures a voltage drop in a drive transistor LS to measure the current flowing through the drive transistor LS. The current sense amplifier includes a preamplifier pre-amp, to which a voltage across the drive transistor LS is inputted, and which obtains a positive output and a negative output corresponding to a voltage difference of the inputted voltage across the drive transistor; and a switch sw, which connects the input end of a common mode voltage vcm and the negative output, the common mode voltage vcm serving as the operation reference of the preamplifier pre-amp. A change of the positive output caused by turning on/off the switch sw can be detected.

The present invention is a signal isolation device comprising: a first circulator; a second circulator connected to the first circulator; a first radio frequency switch connected to the second circulator; an adjustable radio frequency limiter connected to the first radio frequency switch; a low noise amplifier connected to the adjustable radio frequency limiter; a bandpass filter connected the low noise amplifier; a power splitter connected the bandpass filter; an attenuator connected to the power splitter; a second radio frequency switch connected to the power splitter; an active filter chain connected to the second radio frequency switch; a third circulator connected to the attenuator and the first circulator; a power detector connected to the third circulator; and a trigger generator connected to the power detector.