Metalized film resistors exhibit a reverse oxidation reaction under DC load conditions, and this reaction is more severe in humid and hot environments. When the resistor is subjected to AC load, if the operating frequency is low, the following series can be chosen: winding resistors, metal oxide film resistors, metal film resistors, carbon film resistors, synthetic film resistors, and composite core resistors.

When operating frequencies exceed several tens of kHz, high-frequency characteristics must be considered. Generally, the drift of thin-film resistors in the metal foil resistor series is three times that of the carbon film resistor series. Therefore, in power derating applications, the carbon film resistor series seems to have a lower drift failure rate than the metal foil resistor series. There is an alloy foil resistor that combines the advantages of both metal foil and wirewound resistors, offering extremely stable resistance values and excellent frequency characteristics. Below 5 GHz operating frequencies, it essentially behaves as a pure resistor, making it commonly used as a standard resistor.

1. Work Frequency

When resistors are applied to AC loads, their frequency characteristics should always be considered. As the frequency increases, the resistance value can significantly deviate from the nominal value due to factors such as distributed capacitance, skin effect, dielectric loss of the resistive body and leads, and inductive effects. The operating frequency of wound resistors is generally not higher than 50kHz, while the operating frequency of non-inductive wound resistors can reach above 1MHz.

2. Resistance Value Stability

If the circuit function requires high stability in resistance values, such as in attenuators, sampling voltage divider circuits, etc., it is important to select resistors based on their different load conditions. When operating under DC loads, the order of preference should be: wound wire resistors, carbon film resistors, metal film resistors, metal oxide film resistors, synthetic film resistors, and composite core resistors.

The series of synthetic film resistors and solid-core resistors rarely experience open-circuit or short-circuit failures, although their resistance values are not very stable. For circuits that are insensitive to tolerance design, using such resistors can prevent sudden failures of the resistors, which in turn can cause equipment failure. Therefore, these two types of resistors are commonly used in circuit designs with high reliability requirements.