In ultrasound equipment, for example, circuits require tight resistor tolerances and excellent tracking. Plane flight controllers or calculators demand precision resistors, while also requiring that components meet tight size constraints. Long-life stability is important for resistor networks in these applications.
Resistor networks are best realized with thin-film resistor technology, which offers the flexibility to implement either standard or custom resistor circuits. For applications requiring high accuracy, ceramic materials are used for substrate material. Resistor networks usually contain from two to 20 resistors. Many circuit designers prefer to use more networks of fewer resistors each to simplify their board routing. Putting the resistors directly adjacent to the amplifiers simplifies board routing and shortens critical trace lengths.
In high-reliability applications, customers need stable resistive elements. In most cases, customers require a resistor component that — after the calibration routine — they can “set and forget.”
It is essential that once the resistor network is in place, the specified resistance values do not fluctuate. In medical and aerospace applications, a typical stability requirement is 10-ppm change annually. Absolute tolerances and tracking ratios are typically ±0.1% and ±0.05%, respectively. Microhm Electronics's LSP series is thin-film resistor networks with tolerance ±0.1% and ±0.05%.
