Cirrus Logic Inc.

Prabir C Maulik

Mandeep Singh Chadha

Chadha S Mandeep

Philip John Crawley

Zhao Kan

A class AB operational amplifier has first and second intermediate differential nodes respectively driving intermediate stage inverting and non-inverting amplifiers to produce a single-ended output voltage, which are provided with a frequency compensating feedback signal at a selected one of the first and second intermediate differential nodes, derived from the single-ended output of the operational amplifier subject to frequency compensation. The frequency compensating feedback signal is generated with the feedback circuitry. The feedback circuitry includes a compensation capacitor connected to the single-ended output and a current mirror circuit connected to the selected one of the first and second intermediate differential nodes of the operational amplifier.

Frequency compensation for single-ended class AB operational amplifiers with fully-differential input stages

A scalable FIR filter architecture that requires fewer computations, less storage registers, and is capable of parallel processing, is presented. The scalable filter architecture reduces the number of computations (e.g., multiplication) by utilizing the inherent symmetry and reduces the number of storage elements required by utilizing what is known as the transpose-form (as compared to direct-form) filter architecture. The filter architecture is scalable to accommodate different complexity levels. In accordance to the present invention, a filter can be scaled up/down by adding/subtracting a processing block to/from the existing structure. Because these processing blocks can process signals independently and simultaneously, the filter architecture in accordance to the present invention allows for parallel and distributive processing thereby meeting the required performance requirements.

Efficient and scalable FIR filter architecture for decimation

A signal processing circuit includes a main input sampling structure with an integrator operational amplifier and input lines including a switched capacitor. The input lines have switched connections to input signal lines and reference signal lines. A replica sampling structure is used in combination with the main input sampling structure to eliminate or reduce signal-dependent current that is drawn from the input signal line and the reference signal line. The replica sampler includes buffered input lines and switched capacitor of the input sampling structure but the capacitors have switched connections to the reference signal lines such that the connections have opposite polarity to the connections of the reference signal line to the input sampling structure. The replica sampler eliminates or reduces signal-dependent current from the reference signal lines. Buffering of the input lines in the replica sampler eliminates or reduces the signal-dependent current drawn from the input signal lines. The structure efficiently allows the use of a smaller capacitance for the same performance.

Input sampling structure for delta-sigma modulator

A technique for providing a start-up circuit for a bandgap reference. An amplifier configured in a differential arrangement as the bandgap reference. A start-up circuitry ensures that a second input node is maintained at a lower voltage than a first input node of the amplifier at start-up, when the output node corresponding to the second input side of the amplifier is also pulled low.

Robust start-up circuit for CMOS bandgap reference

A technique for performing gain calibration on an analog-to-digital converter (ADC) in which offset errors are canceled during gain calibration. In an ADC having a differential integrator at the input of a modulator, two calibration measurements are obtained at the output, one based on a calibration input and the second based on the reversal of the input polarity. The two measured outputs are subtracted from each other so that offset errors introduced by the converter during gain calibration are cancelled.

Accurate gain calibration of analog to digital converters

A technique for separating an operation of a digital stage into separate noise generation periods in order to time the generation of noise from the digital stage. The invention is utilized in a mixed-signal integrated circuit having analog and digital signals in which the timing of the noise generation ensures that noise is abated during an analog sampling event.

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Austin, TX, United States of America

Prabir C Maulik