Abstract: This application relates to methods and apparatus for outputting a modulated signal for driving a switching output stage. A modulator circuit includes a digital modulator that receives an input signal modified by a correction signal and outputs the modulated signal. A feedback node receives a feedback signal of the output of the switching output stage and a first filter receives and filters an inverted version of the modulated signal to generate a reference signal, such that the reference signal has gain and phase matching to the feedback signal. The reference signal and the feedback signal are both applied to a summation node to generate an analog correction signal which is input to an ADC. An error loop filter is configured to filter the ADC output to generate the digital correction signal.

Abstract: This application relates to methods and apparatus for switching drivers. The switching driver has first and second switches for selectively connecting an output node to first and second switching voltages respectively to generate a first output voltage. A compensator is configured to receive a first monitor signal indicative of a sum of the first and second switching voltages and a second monitor signal indicative of a difference between the first and second switching voltages and to apply compensation to the input signal based on the first and second monitor signals so as to compensate for variations in the first and second switching voltages from defined nominal values of the first and second switching voltages. A modulator controls a duty cycle of the first and second switches based on the input signal after said compensation has been applied.

Abstract: Circuitry for determining a characteristic of an electrochemical cell having a first electrode and a second electrode, the circuitry comprising: measurement circuitry configured to measure a sense current derived from the first electrode and output a sense signal at an output of the measurement circuitry based on the measured sense current; a filter configured to filter the sense signal to obtain a filtered sense signal; and processing circuitry configured to: estimate a signal noise level in the filtered sense signal; and determine the characteristic of the electrochemical cell based on the signal noise level.

Abstract: Circuitry for determining one or more characteristics of an electrochemical cell comprising a first working electrode and a counter electrode, the circuitry comprising: drive circuitry configured to apply a first stimulus to the first working electrode; measurement circuitry configured to measure a first response at the first working electrode; and processing circuitry configured to: applying compensation to the first response to obtain a first corrected response of the electrochemical cell to the first stimulus; and determine a first characteristic of the one or more characteristics of the electrochemical cell based on the first corrected response, the first characteristic associated with the first working electrode.

Abstract: Circuitry for measuring a characteristic of an electrochemical cell, the circuitry comprising: a comparator having a first comparator input, a second comparator input and a comparator output; a feedback path between the comparator output and the second comparator input configured to provide a feedback signal to the second comparator input; and a loop filter configured to apply filtering to the feedback path to generate the feedback signal, wherein the loop filter comprises the electrochemical cell.

Abstract: Switching transducer driver circuitry for driving a load, the switching transducer driver circuitry comprising: output stage circuitry comprising: a first output stage switch operable to couple the load to a first voltage supply; a second output stage switch operable to couple the load to a second voltage supply; and a third output stage switch operable to couple the load to a controllable third voltage supply, wherein a voltage level of the controllable third voltage supply is based on an input signal to the switching amplifier circuitry.

Abstract: Switching driver circuitry comprising: a first half-bridge configured to switch an output node of the switching driver circuitry between a first supply voltage having a first magnitude and a second supply voltage having a second magnitude that is lower than the first magnitude; a second half-bridge configured to switch the output node between a third supply voltage having a magnitude that is equal to or lower than the second magnitude and a fourth supply voltage having a fourth magnitude that is lower than the third magnitude; and an isolation switch coupled to the first and second half-bridges and operable to isolate the second half-bridge from the first half-bridge.

Abstract: Switching driver circuitry comprising: a first half-bridge configured to switch a first supply voltage having a first magnitude; a second half-bridge configured to switch a second supply voltage having a second magnitude, wherein the first magnitude is greater than the second magnitude; and an isolation switch coupled to the first and second half-bridges and operable to isolate the second half-bridge from the first half-bridge.

Abstract: Circuitry for determining a characteristic of an electrochemical cell having a first electrode and a second electrode, the circuitry comprising: a first capacitor node and a second capacitor node for coupling of a series capacitor therebetween, the first capacitor node for coupling to the working electrode; drive circuitry coupled to the second capacitor node, the drive circuitry configured to apply a first time-varying stimulus to the first electrode via the series capacitor; measurement circuitry configured to determine a sense signal derived from a sense current at the first electrode and output the sense signal at an output of the measurement circuitry; and processing circuitry configured to determine a characteristic of the electrochemical cell based on the sense signal.

Abstract: A method of processing subvocalized speech of a user, the method comprising: receiving an audio signal from an input transducer configured to capture speech of the user; receiving a first motion signal from a first motion sensor configured to detect motion of a jaw or a temporomandibular joint (TMJ) of the user; determining the presence of audible speech in the audio signal; when audible speech is present in the audio signal: correlating the audible speech with first motion data in the first motion signal to generate mapping data mapping the first motion data to the audible speech; when audible speech is not present in the audio signal: determining subvocalised speech of the user based on the first motion data and the mapping data.

Abstract: This application relates to methods and apparatus for compensating for distortion in an output drive signal of a switched-mode amplifier which arises from non-linearity of an inductor in an output path for the drive signal. A distortion predictor is configured to predict the distortion in the output drive signal. The distortion predictor has a current predictor configured to determine a predicted current in the inductor based on, at least, an indication of an input voltage for the inductor. A model then models the distortion based on the predicted current and a corrector determines a correction term based on the predicted distortion that can be additively applied to an input signal to at least partly compensate for the distortion in the drive signal.

Abstract: A microphone device, comprising: a microphone configured to generate an audio signal; a natural speech detection module for detecting natural speech in the first audio signal; wherein, on detection of the natural speech in the first audio signal, the natural speech detection module is configured to output a trigger signal to a speech processing module to process the natural speech in the audio signal.

Abstract: Circuitry for determining an impedance of an electrochemical cell comprising at least one first electrode and a second electrode, the circuitry comprising: drive circuitry configured to apply a stimulus to the electrochemical cell, the stimulus having a stimulation frequency and a stimulation amplitude; and measurement circuitry configured to: measure an output of the electrochemical cell to generate an output signal; separate the output signal into a linear component and a non-linear component; and determine the impedance of the cell based on the linear component of the response.

Abstract: Circuitry for processing an analyte signal obtained from an electrochemical cell, the circuitry comprising: a converter, comprising: a first converter input configured to receive the analyte signal; a second converter input; and a converter output configured to output a converted analyte signal, the converter configured to generate the converted analyte signal in dependence on the analyte signal; a loop filter configured to filter a signal derived from the converted analyte signal to obtain a filtered analyte signal at a filter output; and a feedback path between the filter output and the second converter input.

Abstract: This application relates to an amplifier selectively operable in first or second modes. The first mode is a BTL mode with first and second output drivers (103p, 103n) both active to generate respective driving signals that vary with an input signal. The second mode is an SE mode, where the first output driver (103p) is active to generate a driving signal at and the output of the second driver (103n) is held constant. A controller (201) selectively controls the mode based on an indication of output signal amplitude. In the first mode, a ratio of magnitude of the two driving signals varies with the indication of output signal amplitude, i.e. the magnitudes of the two driving signals may vary so as to be not equal.

Abstract: A method of authenticating an origin of a primary audio signal, the method comprising: receiving the primary audio signal; receiving a reference audio signal from a reference microphone; extracting one or more characteristics from the reference audio signal and the primary audio signal; extracting channel properties of the reference audio signal; comparing the one or more characteristics of the reference audio signal to the one or more characteristics of the primary audio signal; comparing the channel properties of the reference audio signal to expected channel properties of the reference audio signal; and authenticating the origin of the primary audio signal based on the comparison between the one or more characteristics and the comparison of the channel properties of the reference audio signal to the expected channel properties.

Abstract: 1 A method of masking audible sound received at a device, the method comprising: outputting an ultrasonic signal to a transducer, the ultrasonic signal comprising ultrasonic content which, when received at a microphone of the device, is mixed into an audible band of an audio signal generated by the microphone in response to the audible sound and the ultrasonic signal; receiving the audio signal from the microphone; compensating the audio signal in dependence on the ultrasonic signal to obtain a compensated audio signal representing the audible sound.

Abstract: This application relates to methods and apparatus for controlling slew-rate of components for outputting an analogue output signal. Described is a signal processing circuit having a forward signal path for receiving an input signal and outputting an analogue output signal. The signal processing circuit has a first component located in said forward signal path for outputting the analogue output signal. A predictor is configured to predict a required slew-rate for the first component based on the input signal and a controller is configured to controllably vary an output slew-rate limit of the first component based on the prediction of required slew-rate.

Abstract: A signal processing system configured to receive an input signal and generate an output signal, the signal processing system comprising: an analog inference engine; and a learning engine coupled to the analog inference engine, wherein the signal processing system is operable in a first mode of operation and a second mode of operation, wherein: in the first mode of operation, the analog inference engine is operative to apply weights to the received input signal to generate the output signal; and in the second mode of operation, the analog inference engine is operative to receive a test input signal and process the test input signal to generate a test output signal, and the learning engine is operative to update the weights of the inference engine based on the test output signal.

Abstract: Circuitry for characterising an electrochemical cell comprising at least one first electrode and a second electrode, the circuitry comprising: drive circuitry configured to apply a stimulus to the at least one first electrode of electrochemical cell, the stimulus having a first stimulation frequency; and measurement circuitry configured to sample a response of the electrochemical cell to the stimulus at a sampling frequency to generate a digital output signal; and processing circuitry configured to determine an impedance of the cell at the first stimulation frequency based on the digital output signal, wherein a first ratio of the first stimulation frequency to the sampling frequency is substantially equal to a second ratio of a number of oscillations of the stimulus to a number of samples obtained by the measurement circuit over a given time period.