This application relates to method and apparatus for driving acoustic transducers, such as speakers or haptic transducers. A transducer driver circuit (200) has a hysteretic comparator (201) configured to compare, with hysteresis, an input signal (S.sub.IN) received at a first comparator input to a feedback signal (S.sub.FB) received at a second comparator input. Based on the comparison the hysteretic comparator (201) generates a pulse-width modulation (PWM) signal (S.sub.PWM) at a comparator output (206). An inductor (203) is coupled between the comparator output and an output node (204). In use a resistive component (208), which may comprise the transducer (301) is coupled to output node (204). The inductor (203) and resistive component (208) provide filtering to the PWM signal (S.sub.PWM). A feedback path extends between the output node (204) and the second comparator input to provide the feedback signal (S.sub.FB).

Certain aspects of the present disclosure are generally directed to circuitry and techniques for voltage-to-current conversion. For example, certain aspects provide a circuit for signal amplification including a first amplifier; a first transistor, a gate of the first transistor being coupled to an output of the first amplifier and a drain of the first transistor being coupled to an output node of circuit; a first resistive element coupled between a first input node of the circuit and an input of the first amplifier; a second amplifier; a second transistor, a gate of the second transistor being coupled to an output of the second amplifier and a drain of the second transistor being coupled to the output node of circuit; and a second resistive element coupled between a second input node of the circuit and an input of the second amplifier.

A sensor assembly including a capacitive sensor, like a microelectromechanical (MEMS) microphone, and an electrical circuit therefor are disclosed. The electrical circuit includes a first transistor having an input gate connectable to the capacitive sensor, a second transistor having an input gate coupled to an output of the first transistor, a feedforward circuit interconnecting a back-gate of the second transistor and the output of the first transistor, and a filter circuit interconnecting the output of the first transistor and the input gate of the second transistor.

The present disclosure relates to circuitry comprising: amplifier circuitry configured to receive a variable supply voltage, wherein the supply voltage varies according to an output signal of the amplifier circuitry; monitoring circuitry configured to monitor one or more parameters of an output signal of the amplifier circuitry; and processing circuitry configured to receive an indication of the voltage of the variable supply voltage and an indication of the monitored parameters from the monitoring circuitry and to apply a correction to one or more of the monitored parameters to compensate for coupling between the variable supply voltage and the monitoring circuitry.

The processing of audio signals is shown in which a first gain-adjustable amplifier is configured to receive a feed forward signal from an input and a second gain-adjustable amplifier is configured to receive a feedback signal from an output. A gain controller supplies a first gain control signal to the first gain-adjustable amplifier, wherein the gain controller supplies a complementary second gain control signal to the second gain-adjustable amplifier, which may be the reciprocal of the first gain control signal. A first combiner is arranged to combine a first output from the first gain-adjustable amplifier with a second output from the second gain-adjustable amplifier. A plurality of filter elements are configured in parallel, wherein each filter element receives an output from the first combiner. A second combiner combines outputs from the filter elements with the original input signal and the filter elements have mutually different filtering characteristic.

A Class D amplifier module includes a semiconductor chip and n inductors. The semiconductor chip includes n output stages, n high-side drivers, and n low-side drivers. The semiconductor chip and the n inductors are housed in a single package and operate according to a control signal received from an external processor.

In accordance with embodiments of the present disclosure, a method of driving a playback waveform to an electromagnetic actuator by a transducer driving system may include operating the transducer driving system in a first mode wherein the electromagnetic actuator is driven with the playback waveform in a closed loop to form a closed-loop voltage drive system that includes a negative impedance, operating the transducer driving system in a second mode wherein the electromechanical actuator is driven with the playback waveform in an open loop, and operating a mode switch for transitioning the transducer driving system to operate between the first mode and the second mode.

A system for controlling the gain of an input signal in an audio signal amplifier. The system includes a user-operable gain control, and analog and digital circuit elements that together are configured to modify the gain of the input signal in response to the user-operable gain control.

An apparatus and method for improving the efficiency of a D class amplifier, particularly at lower output levels. A class D amplifier having a load with inductance, such as a transducer, is configured to concurrently act as its own buck regulator. A capacitor connected to ground and to both ends of the transducer through switches functions as the buck regulator in connection with the inductance of the transducer, providing the class D amplifier with additional voltage levels such as might be provided by a G/H class amplifier but without the added complexity or expense of the G/H configurations. Better efficiency is possible than that provided by a 100% efficient conventional buck regulator. No envelope detector is required, nor any change to the gain of the digital signal to the class D amplifier. Feedback may be used if desired, but is not required to obtain a high quality output signal.

Disclosed embodiments provide flexible performance, high dynamic range, microelectromechanical (MEMS) multipath digital microphones, which allow seamless, low latency transitions between audio signal paths without audible artifacts over interruptions in the audio output signal. Disclosed embodiments facilitate performance and power saving mode transitions maintaining high dynamic range capability.