A sigma-delta ADC is described including a passive filter with an input coupled to the ADC input and a filter output. A gain stage has an input connected to the filter output. A quantiser has an input connected to the gain stage output and a quantiser output. The passive filter includes a first filter resistor between the filter input and the filter output and a filter capacitor having first terminal coupled to the filter output. A feedback resistor is coupled between the quantiser output and the filter output and receives a negative of the value of the output to provide negative feedback to the filter output. The gain stage has a capacitor and resistor in series, and a gain element connected to the gain stage input and an output connected to the gain stage output. One terminal of the gain stage capacitor is connected to the gain element output.

Reference scaling, op amp balancing and chopper stabilization techniques for delta-sigma modulators of analog-to-digital converters are provided. For reference scaling, unit elements in a feedback digital-to-analog (DAC) converter are driven by a reference voltage or disconnected from active circuitry to realize three DAC levels. While disconnected, the unit elements deliver no charge to the device which results in power saving and a reduction in thermal noise. Op amp balancing involves down-sampling the quantizer output followed by up-sampling on the feedback path and filtering to hold a DAC value of the signal for a duration of a sampling period to generate the feedback signal. Chopper stabilization is performed by chopping an operational transconductance amplifier of the integrator at a chopping frequency equal to the sampling frequency.

A class-D amplifier includes an analog-to-digital converter (ADC) configured to generate a first digital signal based on an analog input signal and a feedback signal received at an input node. A loop filter is configured to modify the first digital signal by moving an error of the ADC out of a predetermined frequency band, and a compensation filter is configured to further modify the first digital signal by introducing one or more poles or zeros, thereby generating a second digital signal. An output circuit is configured to generate an output signal at an output node based on the second digital signal, and the feedback signal is generated from the output signal.

Reference scaling, op amp balancing and chopper stabilization techniques for delta-sigma modulators of analog-to-digital converters are provided. For reference scaling, unit elements in a feedback digital-to-analog (DAC) converter are driven by a reference voltage or disconnected from active circuitry to realize three DAC levels. While disconnected, the unit elements deliver no charge to the device which results in power saving and a reduction in thermal noise. Op amp balancing involves down-sampling the quantizer output followed by up-sampling on the feedback path and filtering to hold a DAC value of the signal for a duration of a sampling period to generate the feedback signal. Chopper stabilization is performed by chopping an operational transconductance amplifier of the integrator at a chopping frequency equal to the sampling frequency.

A class-D amplifier includes an analog-to-digital converter (ADC) configured to generate a first digital signal based on an analog input signal and a feedback signal received at an input node. A loop filter is configured to modify the first digital signal by moving an error of the ADC out of a predetermined frequency band, and a compensation filter is configured to further modify the first digital signal by introducing one or more poles or zeros, thereby generating a second digital signal. An output circuit is configured to generate an output signal at an output node based on the second digital signal, and the feedback signal is generated from the output signal.

A method includes receiving samples of digital to analog converter (DAC), partitioning the samples to unit-DACs based upon previous partitions of inputs to the unit-DACs to cancel out integrated non-linearities of outputs of the DAC caused by the gain mismatches of the unit-DACs, including partitioning samples of DAC input to the unit-DACs through a recursive nth order partitioning algorithm. The algorithm includes, for each DAC input, determining a first partition of the DAC input that would cancel an (n1)th order previously integrated non-linearity, adding an equivalent DAC input of the first partition to the DAC input to obtain a total DAC input, using a first order application of the total DAC input to the inputs of the unit-DACs to yield a second partition of DAC input, summing the first and second partitions generate a final partition, and, based on the final partition, computing non-linearity remainders at each order of integration.

A circuit includes a first integration stage, a quantizer, a second integration stage coupled between the first integration stage and the quantizer, and a digital-to-analog converter (DAC). The first integration stage includes a first input node pair configured to receive a pair of differential analog input signals, and the quantizer is configured to generate a digital signal based on the pair of differential analog input signals and a clock signal. The second integration stage includes a second input node pair, and the DAC is configured to receive the digital signal and output feedback signals to at least one input node pair of the first input node pair or the second input node pair.

The present invention provides a fractional-N frequency synthesizer comprising a divider controller comprising a multistage noise Shaping (MASH) digital delta-sigma modulator comprising L stages, wherein the Lth stage is configured to receive as an input a high amplitude dither signal.

A delta-sigma modulator including force circuitry that receives an output digital signal and provides a forced digital signal with a predetermined force state based on a force control signal, a combiner that subtracts the forced digital signal from the output digital signal for providing a digital error signal, and force correction circuitry that converts the digital error signal into one or more analog error correction signals applied to corresponding inputs of loop filter circuitry. The digital error signal and the force control signal may each be used to develop corresponding analog feedback signals used to adjust an analog input signal. The digital error signal may also be converted to one or more correction signals applied to corresponding inputs of the loop filter circuitry to correct the output digital signal. The digital error signal may also be used by a digital noise cancellation filter to further correct the output digital signal.

A sigma-delta ADC is described including a passive filter with an input coupled to the ADC input and a filter output. A gain stage has an input connected to the filter output. A quantiser has an input connected to the gain stage output and a quantiser output. The passive filter includes a first filter resistor between the filter input and the filter output and a filter capacitor having first terminal coupled to the filter output. A feedback resistor is coupled between the quantiser output and the filter output and receives a negative of the value of the output to provide negative feedback to the filter output. The gain stage has a capacitor and resistor in series, and a gain element connected to the gain stage input and an output connected to the gain stage output. One terminal of the gain stage capacitor is connected to the gain element output.