Abstract: An amplifier includes an amplifier chain and a digital correction loop coupled to the amplifier chain. The digital correction loop includes an analog-to-digital (ADC) converter, an averaging filter, and a digital divider. The digital correction loop is configured to generate a correction factor based on ripple or noise in a supply voltage. The amplifier chain is configured to apply the correction factor to an input signal.

Abstract: A method and apparatus are described for bio-impedance measurement using voltage to current conversion. In one example, a bio-impedance transducer includes an input stage to receive a bio-impedance signal having an oscillating voltage from two electrodes, the electrodes being coupled to a body, a resistance across the two electrodes to determine an alternating current of the bio-impedance signal, a gain stage coupled to the resistance to amplify the alternating current, a down converter coupled to the gain stage to convert the amplified alternating current to a direct current bio-impedance signal, and an analog-to-digital converter coupled to the down converter to convert the direct current bio-impedance signal to a digital bio-impedance signal.

Abstract: Embodiments of multi-mode sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a multi-mode sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a controller configured to switch the multi-mode sigma-delta ADC circuit between a single-ended operational mode, a pseudo differential operational mode, and a full differential operational mode to improve common mode rejection (CMR) performance by controlling the pair of OTAs. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.

Abstract: Embodiments of sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a bias compensation circuit configured to measure a biasing condition of a first OTA of the pair of OTAs and to apply the biasing condition of the first OTA to a second OTA of the pair of OTAs to reduce Total Harmonic Distortion Plus Noise (THD+N) in the sigma-delta ADC circuit. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.

Abstract: A method for monitoring and evaluating the photocatalytic activity of a photocatalytic substance is described. The method includes dispersing particles of the photocatalytic substance in a 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) solution to form a photocatalytic suspension; introducing a gas composition to a reactor containing the photocatalytic suspension in the dark to form a purged photocatalytic suspension; illuminating the purged photocatalytic suspension with a light to initiate a photocatalytic reaction and generate a reactive oxygen species (ROS) that is detectable by an electron paramagnetic resonance (EPR) spectrometer; introducing a portion of the purged photocatalytic suspension to the EPR cell in the cavity of the EPR spectrometer to generate an EPR signal and recirculating the portion of the purged photocatalytic suspension back to the reactor; reacting TEMPOL with the ROS to form a EPR silent compound; continuously recording the EPR signal.

Abstract: A method and apparatus are described for a reconfigurable architecture analog front end architecture for electrochemical sensors. In one example, an analog front end includes an electrode driver stage coupled to electrodes of an electrochemical sensor, and measurement channels coupled to the electrode driver stage to receive an electrode signal from the electrodes of the electrochemical sensor and to generate measurement results, the measurement channels configured to switch configurations to perform different measurements.

Abstract: Embodiments of sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a bias compensation circuit configured to measure a biasing condition of a first OTA of the pair of OTAs and to apply the biasing condition of the first OTA to a second OTA of the pair of OTAs to reduce Total Harmonic Distortion Plus Noise (THD+N) in the sigma-delta ADC circuit. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.

Abstract: Embodiments of multi-mode sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a multi-mode sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a controller configured to switch the multi-mode sigma-delta ADC circuit between a single-ended operational mode, a pseudo differential operational mode, and a full differential operational mode to improve common mode rejection (CMR) performance by controlling the pair of OTAs. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.

Abstract: A method and apparatus are described for a reconfigurable architecture analog front end architecture for electrochemical sensors. In one example, an analog front end includes an electrode driver stage coupled to electrodes of an electrochemical sensor, and measurement channels coupled to the electrode driver stage to receive an electrode signal from the electrodes of the electrochemical sensor and to generate measurement results, the measurement channels configured to switch configurations to perform different measurements.

Abstract: A method and apparatus are described for bio-impedance measurement using voltage to current conversion. In one example, a bio-impedance transducer includes an input stage to receive a bio-impedance signal having an oscillating voltage from two electrodes, the electrodes being coupled to a body, a resistance across the two electrodes to determine an alternating current of the bio-impedance signal, a gain stage coupled to the resistance to amplify the alternating current, a down converter coupled to the gain stage to convert the amplified alternating current to a direct current bio-impedance signal, and an analog-to-digital converter coupled to the down converter to convert the direct current bio-impedance signal to a digital bio-impedance signal.

Abstract: A signal generator includes a first voltage generator, a second voltage generator, an operational amplifier, and an oscillator. The first voltage generator generates a first voltage, and the second voltage generator generates a second voltage. The operational amplifier generates an amplified error signal based on the first voltage and the second voltage, and the oscillator generates a periodic signal based on the amplified error signal. The first voltage generator and the second voltage generator are configured to generate their respective voltages based on the periodic signal. As a result, frequency deviation in the periodic signal may be corrected, for example, without increasing the source current of the oscillator or the gain of the operational amplifier. Also, improved phase noise performance may also be achieved through an increase in loop gain.

Abstract: A signal converter includes a first converter, a second converter, a signal generator, and a controller. The first converter generates a first analog signal from a digital signal, and the second converter generates a second analog signal from the digital signal. The signal generator outputs a converted analog signal based on the first analog signal and the second analog signal. The controller generates one or more control signals to change a power supply state of at least one of the first converter and the second converter. The change in power supply state suppress even order harmonics.