Method and apparatus for measuring an output signal of a floating transducer
First Claim
1. A circuit for measuring a voltage output across a voltage transducer that is substantially isolated from a fixed potential, comprising:
- an op amp having differential inputs and a voltage output;
a coupling circuit that is substantially isolated from said fixed potential and that selectively couples said voltage output across said voltage transducer to said differential inputs of said op amp;
a voltage to current converter that receives said voltage output of said op amp and that generates a current output;
a current feedback circuit that feeds back said current output from said voltage to current converter to said differential inputs; and
a voltage measuring device that receives said feedback current from said current feedback circuit and that generates a voltage measurement, which is referenced to said fixed potential, of said voltage output across said voltage transducer.
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Abstract
A circuit for measuring signal output of a transducer includes an amplifier having a differential input and a single ended output referenced to a fixed potential. One transducer terminal is coupled through a source follower to an input terminal of the differential input and the other transducer terminal is coupled through a source follower and a resistive element to the other input terminal of the differential input whereby the transducer terminals are isolated from the fixed potential. A voltage to current converter converts the voltage at the single ended output to an output current that is applied to an input branch of a current mirror. A first output branch of the current mirror supplies a current equal to the converter output current to one terminal of the differential input. A second output branch of the current mirror supplies a current equal to the converter output current to the other terminal of the differential input. A third output branch of the current mirror supplies a multiple of the converter output current to a resistive element having a terminal connected to the fixed potential.
15 Citations
12 Claims
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1. A circuit for measuring a voltage output across a voltage transducer that is substantially isolated from a fixed potential, comprising:
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an op amp having differential inputs and a voltage output;
a coupling circuit that is substantially isolated from said fixed potential and that selectively couples said voltage output across said voltage transducer to said differential inputs of said op amp;
a voltage to current converter that receives said voltage output of said op amp and that generates a current output;
a current feedback circuit that feeds back said current output from said voltage to current converter to said differential inputs; and
a voltage measuring device that receives said feedback current from said current feedback circuit and that generates a voltage measurement, which is referenced to said fixed potential, of said voltage output across said voltage transducer. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A circuit for measuring a voltage output across a voltage transducer that is substantially isolated from a fixed potential, comprising:
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differential amplifying means having differential inputs and a voltage output for amplifying a signal input thereto;
coupling means that is substantially isolated from said fixed potential for selectively coupling said voltage output across said voltage transducer to said differential inputs of said differential amplifying means;
converting means for receiving said voltage output of said differential amplifying means and for generating a current output;
current feedback means for feeding back said current output from said converting means to said differential inputs; and
measuring means for receiving said feedback current from said current feedback means and for generating a voltage measurement, which is referenced to said fixed potential, of said voltage output across said voltage transducer. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification