A choke is an inductor that is designed to block high frequency pulses while letting lower frequency pulse through. Their names comes from the choking off or blocking of high frequency signals. There are two classes of chokes, power chokes and RF chokes. Power and audio frequency chokes typically have a iron core to increase their inductance and make them more effective filters. RF chokes use iron powder or ferrite beads combined with complex winding patterns to reduce parasitic capacitance and operate effectively at high frequencies. Higher frequency chokes will use non-magnetic or air cores.
The push for smaller and more mobile devices has led to the explosion in options for surface mount types of inductors. Surface mount inductors are often used in DC-DC converters, EMI filtering, energy storage, and other applications. Their small size and footprint make surface mount inductors an essential element in the mobile and portable electronic designer's component toolbox. Surface mount inductors are available with and without magnetic shielding, with current capabilities in excess of 10 amps, and with very low losses. Often surface mount inductors will use an iron or ferrite core or special winding techniques to optimize the performance of the inductor and maintain a small footprint and form factor.
Types of Cores
The core material of an inductor plays a large role in the performance of an inductor. The core material directly impacts the inductance of the inductor and will impact the maximum operating frequency, and current capacity of the inductor. The types of inductor cores include: Air Core - Higher frequency operation due to no core losses but a lower inductance Iron Core - Low resistance with high inductance. Core losses, eddy currents, magnetic saturation and hysteresis limit the operating frequency and current Ferrite Core - Non-conductive ceramic material for higher frequency operation. Magnetic saturation limits the current capacity Torroidal Core - A core shaped like a donut that reduces radiated EMI and provides high inductance Laminated Core - High inductance with lower hysteresis and eddy current losses