| 摘要 |
A precision loop voltage measurement circuit outputs a voltage proportional to the differential voltage across a telephone wireline pair. This voltage is coupled to a tip-ring sense rectifier circuit having complementary transistor pairs coupled through a sense resistor to a node, which provides a current as of a composite of the tip-ring voltage and transistor voltage drops within the tip-ring sense rectifier circuit. A differential current extraction circuit generates a first current proportional to the sum of the tip-ring voltage plus voltage drops in the tip-ring sense rectifier circuit, and a second current fractionally proportional to only the internal voltage drops in the tip-ring sense rectifier circuit. The scaled currents are combined in an output resistor to produce a single ended output proportional to tip-ring voltage.
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