Examples of amplifiers and n.sup.th-order loop filters thereof are configured to enable fast and robust recovery from saturation, while limiting signal distortion at or near full power delivery across multiple process and temperature corners. An example n.sup.th-order loop filter comprises n series-coupled resistor-capacitor (RC) integrators. In an example, each of the second RC integrator to the (n−1).sup.th RC integrator has a reset mechanism responsive to a reset signal output from a reset controller when an input signal overload condition is detected at the input. Upon detecting the overload condition, each of the third RC integrator to the (n−1).sup.th RC integrator is hard reset, the n.sup.th RC integrator is not reset, and a controlled reset is performed on the second RC integrator to recover from saturation caused by the signal overload condition, while maintaining the output signal below the 1% total harmonic distortion (THD) level at or near full power delivery.

A signal to be amplified is applied to a gate terminal of an amplifier element that amplifies the signal and that is a transistor, the bias circuit includes: a switching element having a first terminal and a second terminal, the first terminal being electrically connected to the gate terminal; and a trap compensation element having a third terminal and a fourth terminal, the third terminal being connected to the second terminal. Further, the bias circuit includes a control circuit to apply a bias voltage to the gate terminal. Further, the bias circuit includes a voltage application circuit to apply a first voltage to the fourth terminal when the signal to be amplified is a transmission signal, and apply a second voltage to the fourth terminal when the signal to be amplified is a reception signal, the second voltage being a negative voltage.

An audio amplifier that implements current mode control without the use of an explicit or separate current mode sensor is disclosed. The audio amplifier may include a pair of feedback loops that provide current from a node located before an inductor of an output filter and current from a node located after the inductor of the output filter to an integrator circuit. The integrator circuit may be formed from existing circuitry of the audio amplifier controller. Thus, current mode control can be implemented without a separate current mode sensor.

A class-D amplifier having an output driver with a first, second, and third driver, the output driver having a first output coupled to the first and third drivers, a second output coupled to the second driver; a sensing resistor coupled in series between the first driver and the first output; and a pulse width modulation (PWM) controller coupled to the inputs of the drivers and configured to receive an audio input signal; control a PWM generator to generate a first pulse signal and a second pulse signal based on the audio input signal and a power supply input; determine a voltage drop across the sensing resistor; and, responsive to the voltage drop being greater than a threshold, sequence control of the first pulse signal to the first driver and switch a voltage at the first driver to an increased voltage based on the voltage drop.

In some embodiments, an output driver can include a first driver circuit configured to operate with a first supply voltage and generate an output signal having an amplitude in a first range, and a second driver circuit configured to operate with a second supply voltage and generate an output signal having an amplitude in a second range. The output driver can further include a controller configured to operate any one of the first and second driver circuits, such that an output signal of the output driver has an amplitude in an overall range that includes the first and second ranges, and a switch circuit implemented to isolate one driver circuit from another driver circuit when the driver circuit is inactive and the other driver circuit is active.

Amplifying a signal includes outputting an output signal from a Class D amplifier configured to operate as a current driver to a load, such as a loudspeaker, the output of the Class D amplifier controlled by a feedback loop, and, in the feedback loop: performing analog filtering using an active analog filter on an error signal that is based on the output of the Class D amplifier and a reference signal, digitizing a filtered output of the analog filter to produce a sequence of digital values, performing digital filtering on the sequence of digital values to produce a sequence of filtered digital values, and generating a pulse signal to control the output of the Class D amplifier based on the sequence of filtered digital values. The digital filter reduces a destabilizing effect of the loudspeaker's inductance. Associated circuits, systems, modules and electronic devices are disclosed.

An amplifier system may include a first stage having a plurality of inputs configured to receive a differential pulse-width modulation input signal and generate an intermediate signal based on the differential pulse-width modulation input signal, a quantizer configured to generate a modulated signal based on the intermediate signal, a single-ended class-D output stage configured to generate a single-ended output signal as a function of the differential pulse-width modulation input signal, a feedback network configured to feed back the single-ended output signal to a first input of the plurality of inputs and to feed back a ground voltage to a second input of the plurality of inputs, a plurality of buffers, each particular buffer configured to receive a respective component of the differential pulse-width modulation input signal and generate a respective buffered component, and an input network coupled between the plurality of buffers and the first stage. Each particular buffer of the plurality of buffers may include a buffering subcircuit configured to buffer the respective component of the differential pulse-width modulation input signal associated with the particular buffer in order to generate the respective buffered component and a biasing subcircuit configured to limit a magnitude of the respective component of the differential pulse-width modulation input signal driven to circuitry of the buffering subcircuit for driving the respective buffered component.

An amplifier system may include at least one input source, a converter configured to provide voltage rails to an amplifier, the voltage rails including a first voltage rail and a second voltage rail, a MOSFET arranged at a secondary side of the system at the first voltage rail, a second MOSFET arranged at the first voltage rail, a third MOSFET arranged at the second voltage rail, a fourth MOSFET arranged at the second voltage rail; and, a first capacitor arranged at the first voltage rail and a second capacitor arranged at the second voltage rail, the first and forth MOSFETS are configured to operate simultaneously with one another and the second and third MOSFETs are configured to operate simultaneously with one another and opposite of the first and fourth MOSFETs so as to allow synchronous rectification so that the first and second capacitors reciprocally and mutually exclusively charge and discharge.

Apparatus, systems and methods for load-adaptive 3D wireless charging are disclosed. In a 3D charging system of an example embodiment, features comprise a 3D coil design that provides magnetic field distribution coverage for a 3D charging space, e.g.

hemi-spherical space/volume; a push-pull class EF2 PA with EMI filter and transmitter circuitry that provides constant current to the 3D coil, with current direction, phase and timing control capability to adapt to load conditions; reactance shift detection circuitry comprising a voltage sensor, current sensor and phase detector and hardware for fast, real-time, computation of reactance and comparison to upper and lower limits for load-adaptive reactance tuning and for auto-protection; and a switchable tuning capacitor network arrangement of shunt and series capacitors configured for auto-tuning of input impedance, e.g. in response to a X detection trigger signal, which enables both coarse-tuning and uniform fine-tuning steps over an extended reactance range.

An electronic apparatus is described. The apparatus includes a circuit element configured to output a signal comprising a modulated frequency component. The apparatus also includes a filter arrangement comprising first, second and third notch filter arrangements, wherein each of the first and second notch filter arrangements comprise a first series inductor, and a series shunt configuration comprising a second inductor and a capacitor coupled in series and the third notch filter arrangement comprises a series inductor and a shunt capacitor, wherein each of the notch filter arrangements are configured to generate a notch in a frequency response to attenuate the output signal at a frequency of the modulated frequency component.