Abstract:
An implementation of an operational amplifier circuit includes a first stage amplifier circuit, a second stage amplifier circuit and a first feedforward circuit. The first stage amplifier circuit is coupled to a first input node for receiving a first input signal and amplifying the first input signal to generate a first amplified signal. The second stage amplifier circuit is coupled to the first stage amplifier circuit for receiving the first amplified signal and amplifying the first amplified signal to generate a first output signal at a first output node. The first feedforward circuit is coupled between the first input node and the second stage amplifier circuit for feeding the first input signal forward to the second stage amplifier circuit.
Abstract:
Systems and methods for measuring and compensating a DC-transfer characteristic of analog-to-digital converters are described. A test-signal generator comprising a sigma-delta modulator may provide calibration signals to an ADC. An output from the ADC may be filtered with a notch filter to suppress quantization noise at discrete frequencies introduced by the sigma-delta modulator. The resulting filtered signal may be compared against an input digital signal to the test-signal generator to determine a transfer characteristic of the ADC.
Abstract:
Systems and methods for reducing spurious noise tones in sigma-delta analog-to-digital converters (ADCs) are described. A dither signal may be added to two differential input signals of a pseudo-differential sigma-delta ADC. The dither signal may be generated by a pseudo-random bit sequence generator and applied to two input buffers, which add the dither signal to received differential analog input signals. The dithered signals may be digitized by two independent sigma-delta ADCs and then subtracted to remove the dither signal from an overall digital output signal.
Abstract:
Systems and methods for reducing spurious noise tones in sigma-delta analog-to-digital converters (ADCs) are described. A dither signal may be added to two differential input signals of a pseudo-differential sigma-delta ADC. The dither signal may be generated by a pseudo-random bit sequence generator and applied to two input buffers, which add the dither signal to received differential analog input signals. The dithered signals may be digitized by two independent sigma-delta ADCs and then subtracted to remove the dither signal from an overall digital output signal.
Abstract:
An amplifier includes a front-end gain stage and an AC-coupled push-pull output stage. The AC-coupled push-pull output stage includes a first transistor, having a source, a drain and a gate, wherein the source of the first transistor is coupled to a first voltage level; a second transistor, having a source, a drain and a gate, wherein the source of the second transistor is coupled to a second voltage level, the gate of the second transistor is coupled to the front-end gain stage, and the drain of the second transistor is coupled to the drain of the first transistor to form an output terminal of the amplifier; an AC-coupled capacitor, which is a passive two terminal electrical component coupled between the front-end gain stage and the gate of the first transistor; and a resistance component, coupling the gate of the first transistor to a bias voltage level.
Abstract:
A method and apparatus for a digitally-corrected analog-to-digital converter (ADC) are disclosed. The apparatus comprises a nonlinearity generator that generates one or more nonlinear characteristics of a time varying input signal and that causes unwanted signal components at frequencies other than a frequency of the time varying input signal, a frequency response modifier coupled to the nonlinearity generator that modifies the unwanted signal components by altering an amplitude of the unwanted signal components, a frequency response compensator coupled to the frequency response modifier, wherein the frequency response compensator compensates for the modification introduced by the frequency response modifier to provide a filtered digital signal, and an inverse nonlinearity generator coupled to the frequency response compensator for receiving the filtered digital signal, wherein the inverse nonlinearity generator compensates for the one or more nonlinear characteristics.
Abstract:
Systems and methods for measuring and compensating a DC-transfer characteristic of analog-to-digital converters are described. A test-signal generator comprising a sigma-delta modulator may provide calibration signals to an ADC. An output from the ADC may be filtered with a notch filter to suppress quantization noise at discrete frequencies introduced by the sigma-delta modulator. The resulting filtered signal may be compared against an input digital signal to the test-signal generator to determine a transfer characteristic of the ADC.
Abstract:
A filter is provided. The filter receives an input signal and generates an output signal according to the input signal. The filter includes an input network, a high-pass network, and an operational circuit. The first input network provides a first normal path for the input signal to generate a first normal signal. The first high-pass network provides a first high-pass path for the input signal to generate a first high-pass signal. The operational circuit has first and second input terminals. The polarity of the second input terminal is inverse to that of the first input terminal. The operational circuit receives the first normal signal by the first input terminal and the first high-pass signal by the second input terminal such that a subtraction operation is performed on the first normal signal and the first high-pass filter to accomplish a low-pass filtering operation for generating the output signal.
Abstract:
An amplifier includes a front-end gain stage and an AC-coupled push-pull output stage. The AC-coupled push-pull output stage includes a first transistor, having a source, a drain and a gate, wherein the source of the first transistor is coupled to a first voltage level. The AC-coupled push-pull output stage further includes a second transistor, having a source, a drain and a gate, wherein the source of the second transistor is coupled to a second voltage level, the gate of the second transistor is coupled to the front-end gain stage, and the drain of the second transistor is coupled to the drain of the first transistor to form an output terminal of the amplifier. Further, the AC-coupled push-pull output stage includes an AC-coupled capacitor, which is a passive two terminal electrical component coupled between the front-end gain stage and the gate of the first transistor.
Abstract:
A sigma-delta modulator is provided for generating a digital output signal. The sigma-delta modulator includes a multi-stage loop filter, a quantizer, and a digital-to-analog converter. The multi-stage loop filter receives an analog input signal and generates an integrated output signal according to the analog input signal. Each stage of the multi-stage loop filter includes a feedback network. The quantizer receives the integrated output signal and quantizes the integrated output signal to generate the digital output signal. The digital-to-analog converter receives the digital output signal and converts the digital output signal to a compensation signal. The digital-to-analog converter provides the compensation signal to a plurality of internal nodes in the feedback network of the last stage of the multi-stage loop filter.