Patent ID: 7633317

Claim:
A high-side current sense circuit, comprising: a sense resistor having a resistance R sense for connection in series with an input signal having an associated current I and a non-zero DC voltage component such that said sense resistance conducts said current I, said input signal developing voltages V 1 and V 2 on either side of said sense resistance; a differential gain stage powered by first and second fixed supply voltages VCC and VEE, respectively, where VCC>VEE, said gain stage producing an output V o which varies with the difference between the signals presented at its inputs; and a voltage modification circuit comprising: a first resistor having a resistance R 1 connected between V 1 and a first node; a second resistor having a resistance R 2 connected between V 2 and a second node; a first current source which provides a current I CM1 connected between said first node and said supply voltage VEE; and a second current source which provides a current I CM2 connected between said second node and said supply voltage VEE, said first and second resistors and current sources arranged such that R 1 is approximately equal to R 2 and I CM1 is approximately equal to I CM2 ; such that: V 1 ′=V 1 −V CM1 , and V 2 ′=V 2 −V CM2 ; where V CM1 =I CM1 *R 1 and V CM2 =I CM2 *R 2 and V 1 ′ and V 2 ′ are the voltages at said first and second nodes, respectively; said differential gain stage connected at its inputs to said first and second nodes, said voltage modification circuit arranged such that: VEE≦V 1 ′ and V 2 ′≦VCC, and said gain stage and voltage modification circuit arranged such that: V o αI*R sense .