Amplifier common-mode feedback systems for use with switched-capacitor structures
AssigneeAnalog Devices, Inc.
InventorChristopher Michalski
Life of this patent
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Abstract
Improved differential amplifiers are provided for use with switched-capacitor structures. Amplifier embodiments include a differential pair of high-transconductance transistors for generation of differential currents and routing of common-mode feedback signals along an independent path so that sufficient headroom is provided for other high-transconductance transistors that generate common-mode currents. The differential and common-mode currents preferably generate differential and common-mode output signals in finite output impedances of active loads.
Claims27
An amplifier that provides an output signal in response to an input signal, comprising:
- a differential pair of transistors that respond to said input signal and that have first collectors which provide said output signal;
- first and second capacitors serially coupled across said first collectors to provide an error signal Serr;
- and
- first and second feedback transistors that respond to said error signal Serr and have second collectors that are each coupled to a respective one of said first collectors.
A switched-capacitor amplifier that provides an output signal in response to an input signal and corrects a common-mode level of said output signal in accordance with a common-mode reference signal Srefcm and an estimated error signal Serrest, the amplifier comprising:
- a differential pair of transistors that respond to said input signal and that have first collectors which provide said output signal;
- first and second active loads that are each coupled to a respective one of said first collectors;
- first and second capacitors serially coupled across said first collectors to provide an error signal Serr;
- a switched-capacitor network that, in a first operational mode, generates a difference signal Sdiff that represents the difference between said common-mode reference signal Srefcm and said estimated error signal Serrest and, in a second operational mode, couples said difference signal Sdiff across said first and second capacitors;
- and
- first and second feedback transistors that respond to said error signal Serr and have second collectors that are each coupled to a respective one of said first collectors.
A switched-capacitor system that samples an analog input signal in a sample mode and provides a corresponding output signal in a transfer mode, the system comprising:
- a switched-capacitor structure that includes an output capacitor and that acquires a sample signal in said sample mode;
- a differential amplifier coupled across said output capacitor to process said sample signal into said output signal during said transfer mode wherein said differential amplifier includes:
- a) a differential pair of transistors that respond to said sample signal and that have first collectors which provide said output signal;
- b) first and second capacitors serially coupled across said first collectors to provide an error signal Serr;
- and
- c) first and second feedback transistors that respond to said error signal Serr and have second collectors that are each coupled to a respective one of said first collectors.
Dependencies are inferred from the claim text.