Surface Mount Inductors are passive components that are placed during surface mount manufacturing processing. They are positive reactance devices, available in many sizes and form factors optimized for particular applications. They are used in circuits that require filtering, power supplies, and many other functions. Inductance is associated with any PCB trace, via and ground plane and is usually considered a parasitic effect in all passive components and integrated circuits with wire bonds.

Chip inductors are available in all standard chip sizes in multilayer thick film and thin film deposition and wire wound styles. Other inductor types include: Air and Ferrite Cores, Toroidal and Wire-wound. Core can be made of a number of different materials including: Air, Carbonyl Powder, Ceramic, Ferrite, Iron, Metal Composite, Non-Magnetic, Phenolic, Polymer and Powdered Iron.

Important characteristics include the inductor tolerance expressed as a percentage from its nominal value. Current Rating is specified along with Current Saturation - where a core’s magnetic flux reaches a point that an applied magnetic field cannot increase the magnetization of the core further. This point is usually depicted on an inductors ‘BH Curve’ as the sharp transition points on the curve. Signals will become harmonically and parametrically (intermodulation) distorted. It is important to try to keep most inductors below their saturation point as they may begin to dissipate power and heat up. It is extremely important to keep the core at a temperature lower than the Curie Temperature (or Curie Point). This is where thermal effects collapse the materials magnetic properties and typically results in component damage.

DC Resistance is a very important parameter as it determines the I²R power dissipation of the device. Quality Factor (Q) is usually specified at a typical frequency used that is a ratio of the reactive to resistive impedances of the device at that frequency. Self-Resonant Frequency is the frequency where a device’s parasitic capacitive reactance parallel resonates with the inductive reactance.

Inductors used in Power supply lines are typically ferrite beads or chokes (wire wound on a ferrite core) intended to block AC frequencies whilst letting through DC with low impedance. Beads and Chokes are available specifically optimized for high impedance in particular frequency bands. Shielded and unshielded power inductors are available, with shielded inductors typically used for the storage inductor in switching regulators.