Impedance compensation for operational amplifiers used in variable environments
First Claim
1. A circuit for use with an operational amplifier in an environment that experiences fluctuations in ambient energy levels, the operational amplifier including a first input terminal that accepts a first input signal, the first input terminal associated with a first input impedance, a second input terminal that accepts a second input signal, the second input terminal associated with a second input impedance, an output terminal that produces an output signal based on the first and the second input signals, and internal components that generate an input offset voltage and an input bias current, the circuit comprising:
- a compensation impedance stage electrically coupled to at least one of the first input terminal and the second input terminal, the compensation impedance stage having a compensation impedance that is selected proportional to a ratio of a change in the input offset voltage and a change in the input bias current, the compensation impedance compensates for environmentally-induced changes in both the input offset voltage and the input bias current.
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Accused Products
Abstract
A dual compensation operational amplifier is suitable for use in an environment that experiences fluctuations in ambient energy levels. A dual compensation impedance can be determined to nullify or compensate for effects of an input offset voltage or an input bias current or both. Adjustments to the dual compensation impedance can be made based on calibration data for various environmental conditions so that the dual compensation impedance can be either pre-set for anticipated conditions in different target operational environments, or automatically adjusted in-situ. Target operational environments that may benefit from such a dual compensation impedance include remote areas that experience extreme or variable temperatures, high altitudes, space, or high radiation environments.
78 Citations
24 Claims
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1. A circuit for use with an operational amplifier in an environment that experiences fluctuations in ambient energy levels, the operational amplifier including a first input terminal that accepts a first input signal, the first input terminal associated with a first input impedance, a second input terminal that accepts a second input signal, the second input terminal associated with a second input impedance, an output terminal that produces an output signal based on the first and the second input signals, and internal components that generate an input offset voltage and an input bias current, the circuit comprising:
a compensation impedance stage electrically coupled to at least one of the first input terminal and the second input terminal, the compensation impedance stage having a compensation impedance that is selected proportional to a ratio of a change in the input offset voltage and a change in the input bias current, the compensation impedance compensates for environmentally-induced changes in both the input offset voltage and the input bias current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of compensation for fluctuations in ambient energy levels affecting an operational amplifier, the operational amplifier including internal components that generate an input offset voltage and an input bias current, the method comprising:
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determining a change in the input offset voltage caused by a change in ambient energy levels; determining a change in input bias current caused by a change in ambient energy levels; and electrically coupling a compensation impedance stage to at least one input terminal of the operational amplifier, the compensation impedance stage having an impedance selected proportional to a ratio of the determined change in the input offset voltage and the determined change in the input bias current. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A circuit for use with an operational amplifier in an environment that experiences fluctuations in ambient energy levels, the operational amplifier including a first input terminal that accepts a first input signal, the first input terminal associated with a first input impedance, a second input terminal that accepts a second input signal, the second input terminal associated with a second input impedance, an output terminal that produces an output signal based on the first and the second input signals, and internal components that generate an input offset voltage and an input bias current, the circuit comprising:
a compensation impedance stage electrically coupled to at least one of the first input terminal and the second input terminal, the compensation impedance stage having a compensation impedance that is selected as a function of a ratio of a determined change in the input offset voltage due to fluctuations in ambient energy levels and a determined change in the input bias current due to fluctuations in ambient energy levels.
Specification