Amplifying a differential voltage signal component of a voltage across a resistor

1 . An apparatus, comprising:

a resistor;

a differential amplification circuit operatively coupled with the resistor to amplify a differential component of a voltage across the resistor; and

an operative coupling between the resistor and the differential amplification circuit to pass the differential component of the voltage across the resistor and isolate a common mode component of the voltage across the resistor, the operative coupling comprising first switches, second switches, and first and second pairs of capacitors arranged to alternately integrate and transfer charge in a complementary and commutating manner while isolating the common mode component.

2 . The apparatus of claim 1 , the operative coupling comprising:

a first pair of capacitors switchably coupled between a negative input terminal of the differential amplification circuit and the resistor; and

a second pair of capacitors switchably coupled between a positive input terminal of the differential amplification circuit and the resistor.

3 . The apparatus of claim 2 , wherein the first switches to respectively couple the first pair of capacitors with the negative input terminal and to respectively couple the second pair of capacitors with the positive input terminal of the differential amplification circuit; and

the second switches to couple the first and second pairs of capacitors with a first end of the resistor or a second end of the resistor.

4 . The apparatus of claim 3 , wherein respective ones of the first switches are:

coupled between the first pair of capacitors and the negative input terminal of the differential amplification circuit;

coupled between the first pair of capacitors and a controlled common mode voltage source;

coupled between the second pair of capacitors and the positive input terminal of the differential amplification circuit; and

coupled between the second pair of capacitors and the controlled common mode voltage source.

5 . The apparatus of claim 3 , wherein respective ones of the second switches are:

coupled between the first pair of capacitors and the first end of the resistor;

coupled between the first pair of capacitors and the second end of the resistor;

coupled between the second pair of capacitors and the first end of the resistor; and

coupled between the second pair of capacitors and the second end of the resistor.

6 . The apparatus of claim 3 , comprising a logic circuit to generate control signals to selectively turn ON or OFF respective ones of the first switches and the second switches.

7 . The apparatus of claim 6 , wherein control signals generated by the logic circuit cause sets of the first switches and sets of the second switches to alternately integrate and transfer charge at the first and second pair of capacitors in the complementary and commutating manner.

8 . The apparatus of claim 6 , wherein control signals generated by the logic circuit to turn ON and turn OFF the first switches and the second switches are at a predetermined frequency suitable to maintain fidelity of the differential component of the voltage with inputs of the differential amplification circuit.

9 . The apparatus of claim 1 , wherein the differential amplification circuit comprises a first differential amplifier and a second differential amplifier, and respective outputs of the first differential amplifier and the second differential amplifier are coupled to respective ones of positive and negative input terminals of a third differential amplifier.

10 . A method, comprising:

receiving a voltage generated across a resistor; and

providing, via an operative coupling, a differential component of the voltage generated across the resistor to inputs of a differential amplification circuit by: alternately integrating and transferring the differential component, and isolating a common mode component of the voltage generated across the resistor, the operative coupling comprising first switches, second switches, and first and second pairs of capacitors arranged to alternately integrate and transfer charge in a complementary and commutating manner while isolating the common mode component.

11 . A system, comprising:

a direct current sensing circuit; and

an input circuit to sense a voltage signal indicative of a current signal at the direct current sensing circuit, the input circuit to pass a differential component of the voltage signal and isolate a common mode component of the voltage signal, the input circuit comprising first switches, second switches, and first and second pairs of capacitors arranged to alternately integrate and transfer charge in a complementary and commutating manner while isolating the common mode component.