In precision electronics, current-source accuracy is often associated with sophisticated control loops, high-resolution digital-to-analog converters (DACs), and low-noise operational amplifiers. However, real-world performance frequently depends on a less obvious component: the precision resistor. This case study examines how replacing a conventional current-sense resistor with a VPR221Z Z-Foil resistor enabled a high-accuracy current-source design to achieve ultra-low drift,