The circuit of Figure 1 shows a common current
measurement scheme. Current passes through Rsense,
generating a voltage drop, Vrs. Amplifier A1 (configured
with resistors Ri and Rf) magnifies V,, for comparison with
a reference voltage, Vrep In this resistive current
measurement application, a low value sense resistor is
necessary to minimize voltage drop and thus minimize
power loss across the resistor. Unfortunately, a lower value
sense resistor decreases the signal level and increases
sensitivity to several error-inducing circuit parameters. The
following equation summarizes the effects of offset voltage,
sense resistor manufacturing tolerance, kelvin error caused
by trace resistance, and voltage reference error. :