Exar Corporation

Eric Glen Hoffman

Bhupendra K Ahuja

Richard Leigh Gower

J Antonio Salcedo

A programmable gain amplifier having three separately programmable amplifiers. A programmable transconductance amplifier is followed by a programmable transimpedance amplifier, then a programmable switched capacitor amplifier. In one embodiment, this programmable gain amplifier is implemented in an analog front-end (AFE) circuit. One AFE embodiment provides a coarse pre-gain offset a black reference level sampler, and a fine post-gain offset in the programmable switched capacitor amplifier. In one embodiment, an ADC reference is sampled, and is subtracted directly from the video signal in the switched capacitor amplifier so that the zero level of the video signal is made to correspond to the zero level of the ADC. In another embodiment, a piece-wise linear approximation of an exponential gain function is implemented by programming the transconductance and transimpedance amplifiers to provide exponential jumps in gain, while the switched capacitor amplifier is programmed to interpolate as needed between the exponential gain levels.

Image sampling circuit with a blank reference combined with the video input

A method and circuitry for implementing low-power analog-to-digital converters. More particularly, embodiments of the present invention provide an amplifier circuit for pipeline ADCs having multiple stages, some in sample mode, some in hold mode. The stages include residue amplifiers which include a pre-amp and a current source. The current source is turned off during the sample mode. Some embodiments include a second current source that provides a bleeder current during the sample phase so that the pre-amp remains in steady state.

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Fremont, CA, United States of America

Eric Glen Hoffman