Qualcomm Incorporated

Texas Instruments Corporation

The University of Texas System

Intellectual Ventures Holding 81 LLC

Zhiheng Cao

Shouli Yan

Robert Floyd Payne

Xiaohong Li

A digital-to-analog converter (DAC) with a digital segment having a digital data input and an analog segment coupled to the digital segment and having an analog output to output an analog signal corresponding to the digital data. The analog segment includes one or more gain stages and a feedback structure to couple the analog output to the one or more gain stages to attenuate signal distortion at the analog output. A combined gain of the one or more gain stages determines a signal distortion attenuation characteristic of the analog segment.

Low-power digital-to-analog converter

Techniques for designing an efficient power amplifier are described. In one aspect, multiple single unit instance class-D power amplifiers with coupled outputs are utilized to increase efficiency and reduce quantization noise. In another aspect, multiple groups of single unit instance class-D power amplifiers are coupled at the outputs thereof with each group of power amplifiers configured to resonate at unique frequency. This results in increased efficiency and reduction of quantization noise at multiple frequencies bands.

Multi-bit class-D power amplifier system

Methods, circuits and apparatus for biasing an amplifier to maintain consistent operational characteristics over variations in fabrication processes and operational temperature conditions are disclosed. A bias is determined by first comparing output voltages of replica circuits of the amplifier during an offset canceling phase. The output voltages are differently driven by an offset induced by a first reference current and the offset is canceled in response to the first comparing step. The output voltages are secondly compared during a calibration phase and a calibration bias current is adjusted in response to the second comparing step. The amplifier bias is determined based on the calibration bias current. The process is periodically repeated in response to operational variations.

Transconductance bias circuit, amplifier and method

Self-biased bipolar ring-oscillator phase-locked loops with a wide tuning range are disclosed. In a particular example, an apparatus to provide a phase-locked loop is described, comprising a voltage-controlled oscillator (VCO) to provide an output clock signal having a frequency, a quantizer, a phase-frequency detector to generate an adjustment signal, and a charge pump to modify the control voltage. The example VCO includes several ring-oscillator stages, where each ring-oscillator stage includes several gain stages to provide several output currents based on a comparison of a control voltage and several corresponding threshold voltages. The example quantizer includes several comparators to generate digital signals based on the output currents. The example charge pump modifies the control voltage based on the digital signals and the adjustment signal, and includes several switching elements to increase or decrease current to the charge pump based on the digital signals.

Self-biased bipolar ring-oscillator phase-locked loops with wide tuning range

A low-power switched-capacitor circuit is disclosed. The low-power switched-capacitor circuit includes a p-channel switched-capacitor integrator and an n-channel switched-capacitor integrator. The p-channel switched-capacitor integrator includes a first set of input transistors controlled by a first set of capacitors and switches. The n-channel switched-capacitor integrator includes a second set of input transistors controlled by a second set of capacitors and switches. The p-channel switched-capacitor integrator and the n-channel switched-capacitor integrator function together in a push-pull fashion such that a required transconductance as well as width and drain current of the first and second sets of input transistors are reduced by half of those in a conventional switch-capacitor circuit.

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San Diego, CA, United States of America

Zhiheng Cao