Systems and methods for high-sensitivity detection of input bias current
First Claim
1. An apparatus for measuring an input bias current in an operational amplifier, comprising:
- a servo loop;
a low-leakage amplifier connected to the servo loop;
a receptacle for the operational amplifier, the receptacle being configured to couple the operational amplifier to the low-leakage amplifier and to the servo loop when the operational amplifier is mounted in the receptacle;
wherein the servo loop is configured to generate—
a first leakage current of the low-leakage amplifier without the operational amplifier mounted in the receptacle, anda second leakage current of the low-leakage amplifier coupled to the operational amplifier with the operational amplifier mounted in the receptacle, andwherein the input bias current of the operational amplifier is generated by subtracting the first leakage current from the second leakage current.
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Abstract
The invention relates to systems and methods for high-sensitivity detection of input bias current. The invention more particularly relates to platforms and techniques for the calibration and measurement of input bias current in op amps or other devices. In embodiments, the platform can incorporate a servo loop connected to a high-sensitivity test amplifier, such as an instrumentation amplifier. The test amplifier can complete a switchable circuit with the servo loop and detect a calibration input bias current for the test platform, without a production device in place. The device under test can be switched into the servo loop, and the total bias current measured with both the device under test and test amplifier in-circuit. The difference between the measured current with the device inserted and the previously measured calibration current represents the bias current for the subject device, without attaching external meters or requiring reference parts of the production type.
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Citations
28 Claims
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1. An apparatus for measuring an input bias current in an operational amplifier, comprising:
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a servo loop; a low-leakage amplifier connected to the servo loop; a receptacle for the operational amplifier, the receptacle being configured to couple the operational amplifier to the low-leakage amplifier and to the servo loop when the operational amplifier is mounted in the receptacle; wherein the servo loop is configured to generate— a first leakage current of the low-leakage amplifier without the operational amplifier mounted in the receptacle, and a second leakage current of the low-leakage amplifier coupled to the operational amplifier with the operational amplifier mounted in the receptacle, and wherein the input bias current of the operational amplifier is generated by subtracting the first leakage current from the second leakage current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of measuring an input bias current in an operational amplifier, comprising:
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measuring a first leakage current produced by a low-leakage amplifier connected to a servo loop; coupling the low-leakage amplifier to the operational amplifier; connecting the coupled low-leakage amplifier and operational amplifier to the servo loop; measuring a second leakage current produced by the coupled low-leakage amplifier and operational the low-leakage amplifier via the servo loop; and subtracting the first leakage current from the second leakage current to generate the input bias current of the operational amplifier. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification