Nonlinear digital differential amplifier offset calibration
AssigneeHewlett-Packard Development Company, L.P.
InventorsFrederick A. Perner, Kenneth K. Smith
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Abstract
Circuits and methods for calibrating offset error in a differential amplifier in an efficient and reliable way are described. A final calibrated state for the differential amplifier is obtained in accordance with a nonlinear search that requires significantly fewer test stages to complete than linear search methods. As a result, longer test periods may be used with the invention without adversely affecting the overall length of the calibration process. Because circuit conditions near the calibration point cause internal test signals to switch more slowly from one state to another, lengthening the test period time may allow more time for the internal test signals to reach their final values and, thereby, improve calibration accuracy.
Claims20
A circuit for calibrating offset error in a differential amplifier, comprising:
- a memory circuit operable to store a set of programming values selected from a range of multiple possible sets of programming values;
- an output circuit coupled to the memory circuit and operable to place the differential amplifier in a selected calibrated state by applying to the differential amplifier an output calibration signal generated based upon the set of programming values stored in the memory circuit;
- and
- a control circuit coupled to the memory circuit and operable to program the memory circuit with a final set of programming values by progressively narrowing the range of possible programming value sets until the final set of programming values is obtained, the range of possible programming value sets being progressively narrowed in test stages in accordance with a nonlinear search, wherein at each test stage a set of programming values is selected based upon a sensed differential amplifier signal generated in response to a test signal applied to the differential amplifier in a selected calibrated state.
A method of calibrating offset error in a differential amplifier, comprising:
- storing in a memory circuit a set of programming values selected from a range of multiple possible sets of programming values;
- placing the differential amplifier in a selected calibrated state by applying to the differential amplifier an output calibration signal generated based upon the set of programming values stored in the memory circuit;
- and
- programming the memory circuit with a final set of programming values by progressively narrowing the range of possible programming value sets until the final set of programming values is obtained, the range of possible programming value sets being progressively narrowed in test stages in accordance with a nonlinear search, wherein at each test stage a set of programming values is selected based upon a sensed differential amplifier signal generated in response to a test signal applied to the differential amplifier in a selected calibrated state.
Dependencies are inferred from the claim text.