An inductor is a device used to provide inductance, and various coils made of insulated wire are called inductors. Its main function is to block AC while allowing DC to pass through, and to block high frequencies while allowing low frequencies to pass. This means that high-frequency signals encounter significant resistance when passing through the inductor coil, making it difficult to pass, while low-frequency signals experience relatively little resistance, allowing them to pass more easily. The resistance of the inductor coil to DC is almost zero.
Classification of inductance
1. Classified by the nature of the magnetic core: air core coils, ferrite coils, iron core coils, copper core coils.
2. Classified by working nature: antenna coils, oscillation coils, choke coils, notch coils, deflection.
3. Classified by winding structure: single-layer coils, multi-layer coils, honeycomb coils. High-frequency chip ceramic inductors
4. Classified by inductance form: fixed inductance coils, variable inductance coils.
5. Classified by structural characteristics: magnetic core coils, variable inductance coils, color-coded inductance coils, non-magnetic core coils, etc.
Additionally, they are often classified based on operating frequency and overcurrent size, such as high-frequency inductors, power inductors, etc.
Basic applications of inductors
1. The primary function of inductors is to allow direct current (DC) to pass while blocking alternating current (AC), serving mainly to filter, oscillate, delay, and notch in circuits. Inductor coils resist alternating current, and the extent of this resistance is referred to as inductive reactance (XL), measured in ohms. It is related to inductance (L) and the frequency of the alternating current (f) by the formula XL = 2πfL. Inductors can be categorized into high-frequency choke coils and low-frequency choke coils. Tuning and frequency selection: Inductor coils can be connected in parallel with capacitors to form an LC tuning circuit. When the circuit's natural oscillation frequency (f0) matches the frequency (f) of a non-alternating signal, the inductive reactance and capacitive reactance become equal, allowing electromagnetic energy to oscillate back and forth between the inductor and capacitor, leading to resonance in the LC circuit. At resonance, the inductive and capacitive reactances are equal and opposite, minimizing the total inductive reactance of the circuit and maximizing the current (referring to AC signals at f = "f0"). The LC resonant circuit functions to select a specific frequency (f) of an AC signal.
2. Inductors also serve to filter signals, reduce noise, stabilize current, and suppress electromagnetic interference. In electronic devices, magnetic rings are often seen; these magnetic rings, along with connected cables, form an inductor (the wires in the cable are wound around the magnetic ring to create an inductive coil). They are commonly used interference suppression components in electronic circuits, providing excellent shielding against high-frequency noise, hence they are called absorbing magnetic rings, usually made of ferrite material, also known as ferrite magnetic rings (abbreviated as magnetic rings). The impedance of magnetic rings varies at different frequencies. At low frequencies, the impedance is very low, but as the signal frequency increases, the impedance of the magnetic ring increases sharply.
