The gain of an amplifier needs to be as constant as possible, with minimal influence from the outside world. The feedback and sense resistors used in these applications have different heat dissipation and self-heating characteristics. In a differential amplifier we are balancing not just two resistors but four or more; and this means all these devices need to exhibit near-identical behavior over a wide range of values. The Vishay Foil resistor satisfies these requirements better than any other resistive technology