electronic circuits hobbyist,basic electronic circuit design
Ferrite beads and ferrite chokes each have impedance effects that can be harnessed as filters and shields to hold down unwanted interference in electronic circuits. The proper functioning of surrounding circuits can be interfered with by stray high frequency signals, usually called “noise”.
To understand what unwanted noise on top of the main signal is, think about being at a really good party. You are trying to hold a private conversation with someone but it is difficult to hear each other because there is so much ambient noise from the other partiers (circuits) around you. In circuitry, by using electromagnetic coupling, one circuit with very sharp pulses can initiate extraneous signals over the main signal in a nearby circuit, thus becoming a source of noise and causing the receiving circuit to have a problem “hearing” the main signal.
A ferrite bead is a passive electronic component composed of ferromagnetic compounds that contain iron and a small amount of nickel, zinc, or manganese oxides. The impedance qualities of the ferrite choke let it act with high resistance to high frequency signals and low resistance to lower frequency signals, thus muffling the high frequency interference while converting the absorbed energy into a tiny amount of heat.
The amount of suppression possible is dependent of the physical size and shape of the ferrite bead; the type of ferrite material used in the bead will cause the certain range of frequency suppression. The ferrite beads themselves can be a simple pin with a hole in the middle, a single solder blob, or even a multi-layered bead used in surface mount, or SMT, applications. Electromagnetic Interference (EMI) suppression beads, while very much like inductors, are intended to climb in impedance with frequency until they reach a resonance point.
The ferrite bead inductance levels out and maintains good suppression over a broad frequency band, unlike a regular inductor whose impedance would begin to drop with a continued increase in frequency. Computer cables can be one basic application of ferrite chokes. Usually what you see is a bump or long cylinder on the cables that connect the monitor. These are basic snap-on ferrite beads that inhibit the latent RF disturbance from the cables. One everyday use or contemplated use is on cell phones.
One of the great debates of our time is whether the radiation from cell phones will cause brain damage; as a result of this, several products are on the market that are akin to ferrite chokes or shields. These products are designed to hold down the radiation and the interference from your phone. You can distinctly discern this interference if you place your cell phone anywhere near the vicinity of your PC speakers. Those speakers’ cables pick up the energy emitted by the cell phone and an irritating buzzing sound is typically heard.
