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US 7,564,308 B1Granted
Self-biased operational amplifier
AssigneeNational Semiconductor Corporation
InventorSaurabh Vats
Life of this patent
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Abstract
An operational amplifier in accordance with one embodiment of the invention includes folded cascode transistors and a self-biased common-mode feedback circuit coupled to the folded cascode transistors. The operational amplifier can include an output stage coupled to the self-biased common-mode feedback circuit and the folded cascode transistors.
Claims20
An operational amplifier comprising:
- a first folded cascode transistors for receiving currents from a first differential input stage;
- a second folded cascode transistors for receiving currents from a second differential input stage, said second folded cascode transistors coupled to said first folded cascode transistors;
- a buffer stage coupled to said first folded cascode transistors and said second folded cascode transistors;
- a self-biased common-mode feedback circuit coupled to said second folded cascode transistors and said buffer stage;
- and
- an output stage coupled to said self-biased common-mode feedback circuit and said buffer stage.
3 more elements
A method comprising:
- determining if a common-mode voltage of an operational amplifier is increasing, said operational amplifier comprises:
- a first folded cascode transistors for receiving currents from a first differential input stage;
- a second folded cascode transistors for receiving currents from a second differential input stage, said second folded cascode transistors coupled to said first folded cascode transistors;
- a buffer stage coupled to said first folded cascode transistors and said second folded cascode transistors;
- a self-biased common-mode feedback circuit coupled to said second folded cascode transistors and said buffer stage, and
- an output stage coupled to said self-biased common-mode feedback circuit and said buffer stage;
- increasing current through a self-biasing component of said self-biased common-mode feedback circuit if said common-mode voltage is increasing;
- and
- biasing a tail current of a differential comparator stage of said self-biased common-mode feedback circuit after said increasing said current through said self-biasing component.
6 more elements
A differential operational amplifier comprising:
- PNP folded cascode transistors for receiving currents from a first differential input stage;
- NPN folded cascode transistors for receiving currents from a second differential input stage, said NPN folded cascode transistors coupled to said PNP folded cascode transistors;
- a buffer stage coupled to said PNP folded cascode transistors and said NPN folded cascode transistors;
- a self-biased common-mode feedback circuit coupled to said NPN folded cascode transistors and said buffer stage;
- and
- an output stage coupled to said self-biased common-mode feedback circuit and said buffer stage.
3 more elements
Dependencies are inferred from the claim text.