Inductors are components that can convert electrical energy into magnetic energy and store it. The structure of inductor is similar to that of transformer, but there is only one winding. The inductor has a certain inductance, which only blocks the change of current. 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. There are many kinds of inductors, most of which are made of the outer enamel coil surrounding the ferrite spool, while some protective inductors place the coil completely in the ferrite. The cores of some inductive elements can be adjusted. Thus, the inductance can be changed. 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. There are many kinds of inductors with different shapes. The more common ones are: single-layer flat wound hollow core inductors, inter wound hollow core inductors, bodiless hollow core inductors, multi-layer hollow core inductors, honeycomb inductors, inductors with magnetic cores, magnetic can inductors, high-frequency choke coils, low-frequency choke coils, fixed inductors, etc. The winding method of enameled wire of inductance coil on the skeleton can be divided into single-layer winding method and multi-layer winding method. The first winding method: single layer winding method Single layer inductance coil is widely used in today's circuit applications, and its inductance is usually only a few or dozens of micro Heng. The Q value of this kind of coil is generally high, and most of them are used in high-frequency circuits. In the design of single-layer inductance coil, its circuit winding method usually adopts close winding method, intermediate winding method and tire free winding method. These three winding methods are also applicable to different circuit appliances. The second winding method: multi-layer winding method Single layer coil can only be used in occasions with small inductance, so when the inductance is greater than 300 μ H, multilayer coils should be used. The multi-layer winding method can be divided into two types: multi-layer dense winding method and honeycomb winding method: if the coil is wound, its plane is not parallel to the rotating surface, but intersects into a certain angle, this kind of coil is called honeycomb coil. The number of times the wire bends back and forth when it rotates for one cycle is often called the number of turns. The advantages of honeycomb winding method are small volume, small distributed capacitance and large inductance.

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. According to the product characteristics of inductors, it generally includes the following common sense and terms, which you must understand. DC resistance, DC resistance is the resistance value measured under DC. The higher the resistance, the greater the power loss. The smaller the DC resistance of various inductors for resonance, impedance matching and choke, the better. Self resonant frequency refers to the frequency when the coil itself resonates with its own capacitance. If the resonant frequency is exceeded, the inductor will not work. The self resonant frequency of various inductors for resonance, impedance matching and choke shall be greater than the working frequency. DC superposition characteristic refers to the inductance characteristic of superimposing DC current on micro AC current. Allowable current / rated current. Allowable current refers to the maximum DC current that can pass through the coil without damaging the element. If the current exceeds the allowable current, too much heat will be generated and the quality cannot be guaranteed. The allowable current of the choke inductor must be greater than the maximum current when the circuit is working. Working temperature range refers to the allowable range of ambient temperature when the inductor is working. The operating temperature range does not include naturally generated heat. The working temperature range of various inductors for resonance, impedance matching and choke must be within the working temperature range of the equipment. Magnetic saturation, if a magnetic field is applied to magnetic substances such as ferrite, magnetic flux will be generated. The inductance of the inductor depends on the degree of the magnetic flux. The stronger the magnetic field, the smaller the increase of magnetic flux corresponding to the magnetic field. Even if the magnetic field is enhanced, the magnetic flux will not increase. This is the phenomenon of magnetic saturation of magnetic substances. From the point of view of the inductor, as the current through the inductor increases, the magnetic field will also increase, so there will be magnetic saturation of magnetic substances, and as a result, the inductance value will decrease. Since the magnetic saturation characteristics of inductors depend on the type and structure of magnetic materials used by inductors, and inductors used in power supply systems pass a large current, it becomes very important whether magnetic saturation is easy to occur. In order to confirm its degree, refer to the DC superposition characteristics of inductors.

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 structure of inductor is similar to that of transformer, but there is only one winding, which is generally composed of skeleton, winding, shielding cover, packaging material, magnetic core or iron core, etc. If the inductor is in the state of no current passing, it will try to prevent the current from flowing through it when the circuit is connected; If the inductor is in a state of current flow, it will try to maintain the current when the circuit is disconnected. The inductor is composed of coils surrounded by magnetic materials. When the current passes through the inductor, it will create a magnetic field, which does not like to be changed. Therefore, an inductor is an element that will prevent the current flowing through it from changing; If the current flowing through the inductor is constant, the inductor will feel very comfortable and will not create additional force on the charged particles flowing through it. In this case, the inductor behaves like a normal wire. However, if we try to block the current flowing through the inductor, the inductor will create a force to maintain the current flowing through the inductor. If an inductor is connected end to end, and the circuit has no other resistance, in theory, the current can flow forever without decay. However, unless we use superconductors, any wire itself has resistance, which will cause the final current to decay to zero. The greater the resistance in the circuit, the faster the current decay; However, the larger the inductance of the inductor, the slower the current will decay. Once the current decays to zero, the inductor will try to maintain the current status of zero; This is because the inductor always tries to stop the current flowing through it from changing. Therefore, when we connect the inductor to a circuit, at first, the inductor will generate a force, which will prevent the current from increasing.