Switched capacitance voltage differential sensing circuit with near infinite input impedance

摘要

A circuit may sense the differential voltage across two nodes that each have a non-zero common mode voltage. The circuit may have a positive input impedance that is imposed across the nodes. An impedance compensation circuit may generate a compensation current that is delivered to the nodes that substantially cancels the loading effect of the positive input impedance. The impedance compensation circuit may generate a negative input impedance that is imposed across the two nodes that is substantially the same as the positive input impedance. The impedance compensation circuit may instead be configured to deliver the compensation current to the nodes.

主权项

1. A voltage sensing circuit for sensing a differential voltage across two nodes that each have a non-zero common mode voltage, the voltage sensing circuit comprising:
a voltage differential sensing circuit configured to sense the differential voltage across the two nodes that each have the non-zero common mode voltage, the voltage differential sensing circuit having a positive input impedance that is imposed across the nodes when the voltage sensing circuit is connected to the nodes; and an impedance compensation circuit configured to generate a compensation current that is delivered to the two nodes that substantially cancels the loading effect of the positive input impedance on the two nodes.