Inductor basics


An inductor is a coil of wire with a core of either air or a magnetic material such as iron. Inductors oppose changing currents are said to have inductance denoted by L. An inductor allows DC to flow from and blocks AC signal. It has function opposite to the capacitor.

The unit of inductance is Henry(H). The other units such as millihenry (mH) and microhenry (µH) are alternatively used to represent the inductance values. An inductor with a magnetic core has a much larger inductance compare to air cored inductors. More the turns of wire on the coil, more is the value of inductor.

Based on its contruction and usage there are various types of inductors made of iron cores, air cores, iron dust and ferrite cores.

Inductor Impedance

Inductor reactance XL =(2*pi*f*L)
Where, L is in henry, f is in Hz. The inductive reactance will be translated to positive imaginary impedance i.e. impedance at +90 degrees,
In the inductor parameter opposed to AC is referred as inductive reactance XL.
Inductor impedance = 0+i*XL

As per equation, inductive impedance increases either by increasing the inductance (L) or by increasing the A.C. frequency.


High Frequency Inductor

The high frequency inductors are used for radio frequency applications. It offers higher reactance at high operating frequencies and hence inductor will block any such higher radio frequencies. It is used in RF circuits between DC and RF circuit path. This placement helps in passing DC to rf components for biasing. In addition it blocks any high frequencies from RF circuit to prevent damage to power supply. The simple circuit above depicts the same by "RFC". In this circuit RFC (i.e. inductor) passes VCC to MMIC for biasing and blocks RF signal to be amplified towards VCC.

Inductor Manufacturers

There are various manufacturers of inductors which include vishay, coilcraft, coil electronics co. ltd, murata, symcom etc.

Renco Electronics manufacture shielded or unshielded Inductors in the range from 0.1 µH to 180 mH. Renco inductors are available in 14 families and with different shapes which include molded, vaccum impregnated, encapsulated of type radial as well as surface mount.


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