Patent ID: 6617838
Filing Date: 2003-09-09
Classification: G01R,H03F

Abstract:
A current measurement circuit, comprising:a sensing element having a resistance R which carries a current I and develops a voltage V across it which varies with I*R, a first pair of cross-coupled switches which have respective input terminals and output terminals and which are operated with respective control signals, said input terminals connected to receive a voltage representative of said voltage V, a second pair of cross-coupled switches which have respective input terminals and output terminals and which are operated with respective control signals, a pair of input capacitors, each of which has a capacitance Cin and is connected between a respective one of said output terminals of said first pair of cross-coupled switches and a respective one of said input terminals of said second pair of cross-coupled switches, a differential amplifier having inverting and non-inverting inputs and outputs, said inverting and non-inverting inputs connected to respective ones of said output terminals of said second pair of cross-coupled switches, a pair of feedback capacitors, each of which has a capacitance Cf, one of which is connected between the inverting output and non-inverting input of said differential amplifier and the other of which is connected between the non-inverting output and inverting input of said differential amplifier, and a control circuit connected to provide said control signals to said first and second pair of cross-coupled switches and arranged to operate said first and second pair of cross-coupled switches in accordance with a switching cycle during which the connections between said first pair of cross-coupled switches and said input capacitors are interchanged, after which the connections between said second pair of cross-coupled switches and said differential amplifier's inputs are interchanged, such that said voltage representative of said voltage V is sampled on said input capacitors and transferred to said feedback capacitors to produce a differential output voltage Vout from said differential amplifier given by: Vout=N*[(Cin/Cf)*2(I*R)]where N is the number of consecutively performed switching cycles.