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US 8,427,122 B2Granted
Enhancement of power supply rejection for operational amplifiers and voltage regulators
AssigneeMediaTek Singapore Pte. Ltd.
InventorUday Dasgupta
Life of this patent
Estimating the term…
Abstract
A scheme for enhancement of the power-supply ripple rejection for operational amplifiers (op-amps) and low-dropout (LDO) voltage regulators is described. The scheme adds calculated amounts of current derived from the power-supply ripple with the input differential pair current to cancel off the output ripple, improving the high-frequency power-supply ripple rejection without requiring a substantial redesign of the circuitry involved.
Claims16
An electronic circuit with enhanced power supply rejection, the electronic circuit comprising:
- a cancellation circuit comprising:
- an input terminal receiving a reference signal;
- a first capacitor directly coupled to the input terminal for receiving the reference signal and generating a first input current;
- a second capacitor directly coupled to the input terminal for receiving the reference signal and generating a second input current;
- and
- a differential current amplifier comprising:
- a first input for receiving the first input current from the first capacitor;
- a second input for receiving the second input current from the second capacitor;
- a first output for outputting a first output current;
- and
- a second output for outputting a second output current;
- and
- an output terminal generating a cancellation current comprising the first output current and the second output current;
- and
- a regulator circuit comprising:
- a differential pair of transistors outputting a differential current;
- a load coupled to the differential pair of transistors, the load comprising:
- a first input receiving the cancellation current;
- a second input receiving the differential current;
- and
- an output outputting the sum of the cancellation current and the differential current;
- and
- a pass transistor having an input terminal coupled to the output of the load and an output terminal for generating an output current based on the sum of the cancellation current and the differential current.
20 more elements
An electronic circuit with enhanced power supply rejection, the electronic circuit comprising:
- a cancellation circuit comprising:
- an input terminal receiving a reference signal;
- a first capacitor directly coupled to the input terminal for receiving the reference signal and generating a first input current;
- a second capacitor directly coupled to the input terminal for receiving the reference signal and generating a second input current;
- a differential current amplifier comprising:
- a first input for receiving the first input current from the first capacitor;
- a second input for receiving the second input current from the second capacitor;
- a first output for outputting a first cancellation current;
- and
- a second output for outputting a second cancellation current;
- and
- an output terminal generating a cancellation current comprising the first cancellation current and the second cancellation current;
- and
- a regulator circuit comprising:
- a differential pair of transistors outputting a differential current comprising a first differential current and a second differential current;
- a load coupled to the differential pair of transistors, the load comprising:
- a first input for receiving the sum of the first cancellation current and the first differential current;
- a second input for receiving the sum of the second cancellation current and the second differential current;
- and
- a single output outputting the sum of currents received through the first and second inputs of the load, wherein the load adds the currents received through the first and second inputs of the load before outputting the sum of currents as a load output current;
- and
- a pass transistor having an input terminal coupled to the output of the load and an output terminal for generating an output current based on the load output current.
19 more elements
Dependencies are inferred from the claim text.