Inductors mainly play the role of filtering, oscillation, delay, notch, etc. in the circuit, as well as screening signals, filtering noise, stabilizing current and suppressing electromagnetic wave interference.
The most common function of inductance in circuit is to form LC filter circuit together with capacitance. The capacitance has the characteristics of DC resistance and AC connection, while the inductance has the functions of DC connection and AC resistance:
DC connection: it means that the inductor is closed to DC. If the resistance of the inductance coil is ignored, the DC can pass through the inductor unimpeded. For DC, the resistance of the coil itself is very small, and the blocking effect on DC is very small, so it is often ignored in circuit analysis.
AC resistance: when AC passes through the inductive coil, the inductor hinders AC. what hinders AC is the inductive reactance of the inductive coil.
Inductance can be made of conductive material coiled around the magnetic core, typically copper wire, or the magnetic core can be removed or replaced with ferromagnetic material. The core material with higher permeability than air can restrict the magnetic field more closely around the inductive element, thus increasing the inductance.
The small inductor can be directly etched on the PCB board with a method of laying spiral tracks. Small value inductors can also be used to make transistors. The same process is used in integrated circuits. In these applications, aluminum interconnects are often used as conductive materials. No matter what method is used, based on the actual constraints, the most widely used is a circuit called "spinner", which uses a capacitor and an active element to show the same characteristics as the inductive element. Inductive elements used to isolate high frequencies are often composed of a metal wire passing through a magnetic column or bead.
The inductor is generally composed of skeleton, winding, shielding cover, packaging material, magnetic core or iron core, etc.
Skeleton generally refers to the support for winding coils. For some fixed inductors or adjustable inductors with large volume (such as oscillation coil, choke ring, etc.), most of them wrap enameled wire (or yarn wrapped wire) around the skeleton, and then install the magnetic core, copper core, iron core, etc. into the inner cavity of the skeleton to improve its inductance.
Winding refers to a group of coils with specified functions, which is the basic component of inductor. The winding can be divided into single layer and multi-layer.
The magnetic core and magnetic rod are generally made of nickel zinc ferrite (NX Series) or manganese zinc ferrite (MX Series) and other materials, which have "I" shape, column shape, cap shape, "e" shape, tank shape and other shapes.