The present disclosure relates to a magnetic field sensor circuit including at least one coil for measuring a magnetic field, a first stage amplifier circuit coupled to the coil and having a first transfer function with a pole at a first frequency, and a second stage amplifier circuit coupled to an output of the first stage amplifier circuit and having a second transfer function with a zero at the first frequency. In some embodiments, a temperature dependent frequency drift of the pole of the first transfer function corresponds to a temperature dependent frequency drift of the zero of the second transfer function.

An apparatus for amplifying an audio source includes a speaker and a chip. The chip includes a processor configured to generate a signal and an amplifier element configured to amplify the signal into an amplified signal. The chip further includes a current monitor configured to monitor the current of the amplified signal prior to the amplified signal being output from the chip to the speaker and a voltage monitor configured to monitor the voltage of the amplified signal prior to the amplified signal being output from the chip to the speaker. The processor of the chip is configured to control a power of the amplified signal output from the chip to the speaker based at least on the current and the voltage.

A power amplifier device includes: a first power supply terminal for inputting a first power supply voltage; a first transistor for power amplification that (i) includes a first gate to which a bias voltage is applied, and (ii) is supplied with power from the first power supply terminal; a second power supply terminal for inputting a second power supply voltage lower than the first power supply voltage; a second transistor for monitoring that (i) includes a second gate to which the bias voltage is applied, (ii) is supplied with power from the first power supply terminal or the second power supply terminal, and (iii) imitates an operation of the first transistor; and a bias circuit that is supplied with power from the second power supply terminal and generates and adjusts the bias voltage according to a drain current or a source current of the second transistor.

A Class-D amplifier that includes a driver stage operable in a plurality of modes having different respective output impedances, a loop filter having an output, and a circuit configured to sense a current at a load of the Class-D amplifier, determine, based on the sensed current, an IR drop for a respective output impedance of the driver stage, and add the IR drop to the loop filter output to compensate for the respective output impedance of the driver stage to reduce distortion.

A dynamically stabilizable amplifier drives an output current into an RLC load. A driver stage generates the output current, and a control circuit compares a current level of the amplifier output with a threshold and selectively enables a stabilizing resistor (to selectively shunt the load or dampen in series with the load, depending on RLC load type) at the driver stage output based on the comparison so that the amplifier is stable across a range of the output current level. The control circuit disables the resistor when the output current is above the highest threshold and enables it when below. The control circuit may control the resistor to have one of multiple resistance values based on a comparison with multiple thresholds. The output current level may be determined by replicating the output current level or by an input current level that sets the output current level independent of the load.

A method and a system for monitoring operation of at least one loudspeaker in a system comprising a plurality of loudspeakers connected in series on a same amplifier output in at least one loudspeaker chain driven by an amplifier board, the method comprising measuring a current consumed by the amplifier in an operating position of the plurality of loudspeakers, yielding a reference current; stopping the masking system into an idle position; emitting the reference signal, measuring an idle current consumed by the amplifier; and comparing the idle current with the reference current. The system comprises a microprocessor unit and a current measurement module, wherein the current measurement module is configured to measure a current drawn by the amplifiers and feed a resulting signal to the microprocessor unit; and the microprocessor unit generates an output signal to respective output channel.

A system may include a Class-D stage comprising a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage, a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage, a first low-side switch coupled between a ground voltage and the first output terminal, and a second low-side switch coupled between the ground voltage and the second output terminal. The system may also include current sensing circuitry comprising a first sense resistor coupled between the first low-side switch and the ground voltage, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the first sense resistor when the first low-side switch is activated. The current sensing circuitry may also include a second sense resistor coupled between the second low-side switch and the ground voltage, such that an output current through the load causes a second sense voltage proportional to the output current across the second sense resistor when the second low-side switch is activated. The system may also include measurement circuitry configured to measure the first sense voltage and the second sense voltage to determine the output current.

A system may include a Class-D stage comprising a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage, a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage, a first low-side switch coupled between a ground voltage and the first output terminal, and a second low-side switch coupled between the ground voltage and the second output terminal. The system may also include current sensing circuitry comprising a sense resistor, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor. The system may additionally include a modulator for generating a differential pulse-width modulation driving signal to the first high-side switch, the second high-side switch, the first low-side switch, and the second low-side switch and pilot tone injection circuitry configured to inject a periodic pilot tone into the differential pulse-width modulation driving signal at a pilot tone frequency.

An amplifier overload power limit circuit, system, and a method thereof comprising a monitoring of a current gain of a BJT based on a current detector and limiting power to the BJT based on the monitored current gain to prevent the BJT from driven into a saturation mode and the amplifier overdrive.

A sense amplifier circuit comprising a first-, second-, third- and fourth-amplification-blocks, each amplification-block comprising: an amplification-block-transistor comprising and an amplification-block-resistor. The amplification-block-transistor includes: a first-conduction-channel-terminal, a second-conduction-channel-terminal that is connected to an amplification-block-output-node, and a control-terminal that is connected to an amplification-block-control-node. The sense amplifier circuit also comprises: an amplification-block-resistor connected in series between an amplification-block-input-node and the first-conduction-channel-terminal; a first-bias-voltage-source connected to the amplification-block-control-nodes of the first- and third-amplification-blocks, a second-bias-voltage-source connected to the amplification-block-control-nodes of the second- and fourth-amplification-blocks. The sense amplifier circuit also comprises: a first-common-mode-voltage-resistor connected in series between a first-sensed-output-terminal and a common-mode-voltage-node; and a second-common-mode-voltage-resistor connected in series between a second- sensed-output-terminal and the common-mode-voltage-node.