Custom Made Ultra-Miniature High Current Surface Mount Square Air
Core Inductors 5.5 to 27nH For RF Circuits
Description
Square Air Core RF Inductors, part of the wound air core inductor
family, are ideal for RF circuits, broadband I/O filtering,
frequency selection, or impedance matching. The unique square cross
section of the air core inductor provides better performance, and
offers manufacturing advantages over toroidal coils.
Model Example
| 1 | 2 |
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Wire diameter:0.8mm ID 5mm;Turn:1.5 turn; Length:6mm | Wire Diameter:1.2mm ID 4mm;Turn:4 turn;Length:11mm |
Typical Applications
RF Applications
RF Circuits
Broadband I/O Filtering
Impedance Matching
Features & Benefits
Square cross section construction
Available in 0806, 0807, and 0908 sizes
20 Inductance values ranging from 5.5nH to 27.3nH
High Q
High Current
Excellent SRF
Customized available
L versus Frequency Curve
What is an air core coil?
We'll use the term 'air core coil' to describe an inductor that
does not depend upon a ferromagnetic material to achieve its
specified inductance. This covers the cases where there really is
just air inside as well as windings upon a different insulator such
as bakelite, glass or PTFE etc.
Do you need an air coil?
What are the advantages of an air core coil?
Its inductance is unaffected by the current it carries. This
contrasts with the situation with coils using ferromagnetic cores
whose inductance tends to reach a peak at moderate field strengths
before dropping towards zero as saturation approaches. Sometimes
non-linearity in the magnetization curve can be tolerated; for
example in switching converters. In circuits such as audio cross
over networks in hi-fi speaker systems you must avoid distortion;
then you need an air coil. Most radio transmitters rely on air
coils to prevent the production of harmonics.
Air coils are also free of the 'iron losses' which affect
ferromagnetic cores. As frequency is increased this advantage
becomes progressively more important. You obtain better Q-factor,
greater efficiency, greater power handling, and less distortion.
Lastly, air coils can be designed to perform at frequencies as high
as 1 Ghz. Most ferromagnetic cores tend to be rather lossy above
100 MHz.
And the 'downside'?
Without a high permeability core you must have more and/or larger
turns to achieve a given inductance value. More turns means larger
coils, lower self-resonance and higher copper loss. At higher
frequencies you generally don't need high inductance, so this is
then less of a problem.
Greater stray field radiation and pickup. With the closed magnetic
paths used in cored inductors radiation is much less serious. As
the diameter increases towards a wavelength (lambda = c / f), loss
due to electromagnetic radiation will become significant. Balanis
has the gory details. You may be able to reduce this problem by
enclosing the coil in a screen, or by mounting it at right angles
to other coils it may be coupling with.
You may be using an air cored coil not because you require a
circuit element with a specific inductance per se but because your
coil is used as a proximity sensor, loop antenna, induction heater,
Tesla coil, electromagnet, magnetometer head or deflection yoke
etc. Then an external field may be what you want.
