An apparatus comprises an amplifier having a predefined linear range and a shunt load. The shunt load may be connected to an output, an input, or between gain stages of the amplifier. An impedance of the shunt load dynamically varies in response to a level of a signal presented at a node formed by interconnection of the shunt load and the amplifier, extending linearity of the amplifier beyond the predefined range.

A power amplifier bias circuit with embedded envelope detection includes a bias circuit stage coupled to an envelope detector circuit to increases a bias provided to a power amplifier as a function of an incoming envelope signal. The envelope detector circuit includes a first source/emitter follower transistor, a current source, and a filter to generate a baseband envelope signal. The current source is coupled to an output node of the first source/emitter follower transistor and the filter is also coupled to the output node of the first source/emitter follower transistor. The bias circuit stage includes one or more replica transistors that replicate transistors of the power amplifier or power amplifier core stage, an envelope detector replica transistor and a replica of the current source of the envelope detector circuit.

A predictive brownout prevention system may be configured to prevent brownout of an audio output signal. Particularly, the brownout prevention system may be configured to receive information indicative of adaptive estimates of power supply conditions, wherein the information indicative of adaptive estimates of the power supply conditions comprises information regarding a voltage component and a resistive component received from an adaptive battery model of a battery for providing electrical energy to a power supply for generating the power supply voltage and adapt the adaptive battery model based on a monitored battery voltage output by the battery and loading events of the signal path and excluding loading events of components other than the signal path which are powered from the battery.

A limiter circuit is integrated into an RF power amplifier. The limiter circuit automatically starts adding attenuation at the input of the RF power amplifier after a predetermined input power level threshold is exceeded, thereby extending the safe input drive level to protect the amplifier. In a preferred embodiment of the invention, the limiter circuit is implemented using a pseudomorphic high electron mobility transistor (PHEMT) device or a metal semiconductor field effect transistor (MESFET) device. Diode connected transistors or Schottky diodes may also be used in the limiter circuit.

A radio frequency (RF) switch apparatus includes a signal input terminal; a signal output terminal; a first transistor including a first input terminal connected to the signal input terminal, a first output terminal connected to the signal output terminal, a first gate terminal, and a first body terminal, wherein one of the first input terminal and the first output terminal is a source terminal and another one of the first input terminal and the first output terminal is a drain terminal; a first capacitor circuit connected between the first input terminal and the first body terminal; and a second capacitor circuit connected between the first body terminal and the first output terminal; wherein a first capacitance of the first capacitor circuit is greater than a second capacitance of the second capacitor circuit.

According to an embodiment, a method includes amplifying a signal provided by a capacitive signal source to form an amplified signal, detecting a peak voltage of the amplified signal, and adjusting a controllable impedance coupled to an output of the capacitive signal source in response to detecting the peak voltage. The controllable impedance is adjusted to a value inversely proportional to the detected peak voltage.

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.

According to one mode of the inventive concept, an amplification device includes a first amplification unit configured to amplify an input signal when a power level of the input signal is within a first range, a second amplification unit configured to amplify the input signal when the power level of the input signal is within a second range, and an abnormality sensing unit configured to sense an occurrence of an abnormality in the second amplification unit. The abnormality sensing unit senses reverse power regarding an output of the second amplification unit to generate a sensed voltage and compares the sensed voltage with a reference voltage to sense whether an abnormality occurs in the second amplification unit.

The disclosed embodiments include an audio amplifier system configured to provide a total harmonic distortion (THD) controlled clip detector and an automatic gain limiter (AGL) solution for a closed-loop amplifier. The audio amplifier system is capable of maintaining high power output without hard distortion (i.e., hard clipping) for providing better acoustics, while preventing damage to the system.

The disclosed embodiments include an audio amplifier system configured to provide a total harmonic distortion (THD) controlled clip detector and an automatic gain limiter (AGL) solution for a closed-loop amplifier. The audio amplifier system is capable of maintaining high power output without hard distortion (i.e., hard clipping) for providing better acoustics, while preventing damage to the system.