Inductors

1. Definition

1.1 Inductor

An inductor is a passive two-terminal electronic component that stores energy in a magnetic field when electric current flows through it. It usually consists of a coil of wire wound around a core, which may be air, ferrite, or iron.

types of inductors

Inductor symbol

Inductor symbol

1.2 Inductance

Inductance is the property of an electrical conductor to oppose a change in current by generating a voltage (EMF) proportional to the rate of current change.
It is measured in henries (H), typically in millihenries (mH) or microhenries (µH).

2. Features

  • Measurement: in henries (H), usually mH or µH for practical circuits.
  • Current Rating: maximum continuous current without overheating.
  • DC Resistance (DCR): resistance of the wire; lower DCR means higher efficiency.
  • Saturation Current: the current at which the core material stops storing additional magnetic energy effectively.
  • Core Material: affects performance (air core for high-frequency, ferrite or iron core for power applications).
  • Tolerance: variation from stated inductance value.
  • Physical Size: larger inductors can handle more current and have higher inductance.

4. How to Use

Safety Note

While inductors don’t store charge like capacitors, they can generate high voltage spikes when current is suddenly interrupted. This can damage components or cause electric shock in certain cases. Please handle switching circuits with care.

4.1. Identify the inductor value

  • Look for printed markings or color codes, or use an LCR meter.
  • Values are given in henries (H), millihenries (mH), or microhenries (µH).

inductor value code

4.2. Choose the right inductor

  • Inductance value (determines filtering, timing, or energy storage behavior).
  • Current rating (must exceed the maximum current in the circuit).
  • Core type (air, ferrite, iron powder, laminated steel, etc.).
  • Frequency range (some inductors are optimized for high-frequency RF, others for low-frequency power).

4.3. Connect it correctly

  • Inductors are non-polarized they can be connected in either direction.
  • In series: total inductance is the sum of all inductors. => increases overall inductance.
  • In parallel: total inductance is less than the smallest inductor. => decreases overall inductance, increases current handling.

4.4. Test and verify

  • Use an LCR meter to measure inductance.
  • Check DCR to ensure efficiency.
  • In switching circuits, check for excessive heating.

4.5. Install in circuit

  • On breadboard: insert leads into holes.
  • On PCB: solder into the correct pads, keeping them away from sensitive signal traces if high currents are involved.

5. When to Use

  • Filtering: with capacitors to create LC filters in power supplies and signal processing.
  • Energy Storage: in switch-mode power supplies to store and transfer energy.
  • Chokes: to block high-frequency AC while allowing DC or low-frequency AC to pass.
  • Tuning Circuits: in radio transmitters and receivers to select specific frequencies.
  • Transformers: as part of coupled inductors to step up or step down voltages.

6. Video Explanation

video coming soon