Introduction
Resistors are the most common passive
component on any printed circuit board
(PCB), so it’s good that they cost just a little
more than a penny each. Up in price an
order of magnitude from resistors are
capacitors, which are generally larger. Rare
— except in radio frequency circuits — are
inductors which are generally much larger
than the capacitors, more expensive, and
very hard to source.
Probably not a lot of folks have likely
seen a memristor — the fourth passive
component that completes the passive
component family, as seen in Figure 1.
44 July/August 2018
Does Inductor
Winding Have
You Tied in
Knots?
While resistors and capacitors are easily
procured and stocked, most radio
frequency circuits require inductors in a
wide range of very specific values. In
most cases, you need to create these
yourself, by winding wire on ferrite rods
or toroids of specific types and sizes. Is it
possible to substitute another ferrite
piece at hand and still get the right
inductance value? How can a hobbyist
measure inductance without buying an
expensive instrument? This article
describes the principle behind
inductance and presents some tricks that
I have used to make my own inductors.