Mediatek Corporation

Chi-Lun Lo

Yu-Hsin Lin

Hung-Chieh Tsai

Chen-Yen Ho

Michael Anthony Ashburn, Jr

Frank Op 't Eynde

Khurram Muhammad

Tien-Yu Lo

Chia-Hsin Wu

Jong-Woei Chen

Nathan T Egan

Tsung-Ling Li

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.

Operational amplifier circuits

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.

System and method for measuring the DC-transfer characteristic of an analog-to-digital converter

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.

Digitally-corrected analog-to-digital converters

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.

Sigma-delta ADC with dither

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.

Amplifier, fully-differential amplifier and delta-sigma modulator

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.

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.

A receiving device includes: a mixer module arranged to receive an input signal to generate a down-converted output; a first active filter, the first active filter arranged to receive the down-converted output and perform an active filtering process upon the down-converted output to generate a first filtered output; a passive filter, the passive filter arranged to receive the first filtered output and perform a passive filtering process upon the first filtered output to generate a second filtered output; and a processing circuit, the processing circuit arranged to receive the second filtered output and process the second filtered output to generate an output signal corresponding to the input signal.

Receiving device and method thereof

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.

Filters with order enhancement

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.

Sigma-delta modulators with excess loop delay compensation

An amplifier, a fully-differential amplifier and a delta-sigma modulator are disclosed. The disclosed amplifier includes a front-end gain stage, an AC-coupled push-pull output stage and a compensation circuit. The compensation circuit is coupled between the front-end gain stage and an output terminal of the amplifier. The AC-coupled push-pull output stage uses an AC-coupled capacitor (which is a passive two terminal electrical component rather than a stray or parasitic capacitance of a transistor) to couple the front-end gain stage to a gate of a top or bottom transistor of a push-pull structure introduced in the AC-coupled push-pull output stage, and uses a resistance component to couple a gate of the top or bottom transistor (depending on which one is coupled to the AC-coupled capacitor) to a bias voltage level.

An operational circuit includes: a gain control circuit arranged to provide a gain value upon an input signal according to a set of control signals, wherein the gain control circuit includes a first resistor-based network and a second resistor-based network; an operational amplifier coupled to the gain control circuit and arranged to generate an output signal according to the input signal and the gain value; and a first capacitor coupled to the operational amplifier and arranged to hold the output signal between a first input terminal and a first output terminal of the operational amplifier, wherein when the operational circuit is operating, a first terminal of the first capacitor is consistently coupled to the first input terminal of the operational amplifier, and a second terminal of the first capacitor is consistently coupled to the first output terminal of the operational amplifier.

Track and hold circuit and related receiving device with track and hold circuit employed therein

A DC offset calibration circuit has a first resistor, a first switch, a second resistor, and a second switch. The first resistor is coupled to a first supply voltage. The first switch is coupled to the first resistor, to a first input of an amplifier, and to a first input resistor. A second end of the first input resistor is not coupled to the first supply voltage. The second resistor is coupled to a second supply voltage. The second switch is coupled to the second resistor, to a second input of the amplifier, and to a first end of a second input resistor. A second end of the second input resistor is not coupled to the second supply voltage.

Low-noise DC offset calibration circuit and related receiver stage

A receiver stage has an operational amplifier, a feedback resistor coupled between an output of the operational amplifier and an input of the operational amplifier, and a DC offset calibration circuit. The DC offset calibration circuit includes a plurality of resistors and a plurality of switches. Each resistor has a first end coupled to a supply voltage. First ends of each of the switches are coupled to second ends of each of the resistors, respectively, and second ends of the switches are coupled to the input of the operational amplifier.

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Yangmei, Taiwan

Chi-Lun Lo