converts electric power into radio waves, and then turns radio waves back in electric current. They are usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an oscillating radio frequency electrical current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves).
are a type of transformer (magnetic component made up of two or more windings of copper wire) that is specifically designed to be used in audio circuits. Audio transformers are used to block DC component of an audio signal or radio frequency interference, to provide impedance matching between high and low impedance circuits, or to split or combine audio signals.
are used in electronic circuits to control current flow through the circuit. Capacitors control current by storing electrical energy, then releasing it at a controlled rate. Capacitors are constructed by sandwiching a non-conductive material (dielectric) between two conductive plates.
Dielectrics can be constructed from paper, aluminum, oil, ceramic, tantalum or a number of other materials. There are a great variety of capacitor types consisting of different dielectrics, energy storage capabilities, voltage ratings, packaging variations, tolerance and their ability to withstand adverse electrical and environmental conditions.
A ceramic resonator
is a passive device used for frequency-control, or circuit-timing. The resonator is considered a “piezoelectric” device, and is used in electronic circuits to provide timing for micro-controllers. The resonator has a ceramic element or wafer inside, which oscillates or vibrates at a specific frequency when power is applied. Ceramic resonators provide a rugged alternative to crystals and oscillators.
(sometimes called quartz crystal or clock crystal or crystal resonator) are another type of timing device that uses a quartz crystal element. Crystals provide high accuracy over a broad temperature range. Crystals are smaller in size than an oscillator, that cannot perform at super-high frequencies, under extreme voltage or temperature conditions. However, the crystal can provide highly accurate and highly stable timing, over a broad range of temperatures, for nearly all applications utilizing MPUs (microprocessors), DSPs (digital signal processors) and MCUs (microcontrollers).
The EMI Chip
(3-terminal capacitor filter) is one of the most common and popular EMI solutions. These chips are surface-mount "feed-thru capacitors" that are offered in standard 0805/1206/1806/1812 chip sizes, are non-polar, and are available with relatively high current capability. This particular device is considered a "noise separation" type filter, as it directs the energy of the unwanted noise frequencies to ground.
EMI Feedthrough Filters
The name "feed-thru" originates from the construction of these filters, which usually utilize a feed-thru capacitor or tubular capacitor element as the mainstay component inside of the filter - this is also where the filter size and shape comes from. Feedthrough filters
, in general, are larger, bulkier, panel mount and bolt-in types of filters. There are numerous types of feedthrough filters: Coaxial Filters
, filters with cylindrical shaped case usually containing a combination of capacitors and inductors; Singles
, a single feed-thru that can be mounted by soldering directly to a chassis or bushing; Solder Mount
, a filter with accommodations or a lead configuration that is conducive to soldering; Threaded Bushing Mount / Bolt-In
, utilizes a threaded bushing and can be mounted directly to an enclosure or plate using the hardware or a threaded hole; Surface-Mount Filter
; Filter Arrays & Filter Plates
, assemblies or "collections" of filters mounted together via a metal plate or chassis.
As the frequency and speed at which information is processed today increases, the more susceptible equipment becomes to interference and the more demand there is for EMI suppression products. EMI filters
select or reject a band of frequencies. In communication systems, filters are used to allow
those frequencies containing the desired information to pass and reject the remaining frequencies.
A ferrite bead
is a passive electronic component used to remove unwanted electrical noise (EMI). It is sometimes referred to as a surface-mount ferrite bead, a ferrite bead, a chip bead, EMI bead core, leaded ferrite bead inductor, leaded ferrite bead. These devices are offered in leaded or SMT versions, arrays, and packaged in bulk or tape and reel. Ferrites are the least expensive and simplest method of eliminating EMI - given their moderate filtering is up to the job at hand. In cases where 5dB or less of "cleanup" is required, a ferrite bead may be a sufficient solution. The most common applications include DC power line and general and high-speed signal line filtering. Ferrite beads are a noise limiting filter type, meaning they dissipate the energy of the unwanted frequencies in the form of heat - not to ground.
is a length of conductor, normally wire, wound into a coil (thus the nickname that some people call this device) and around a core to concentrate the magnetic force (field) and maximize the inductance. The more turns of wire in the coil, the higher the inductance value. Inductors can be found in all facets of electronic design so they are not specific to one application area. Its primary properties are to resist changes in AC (alternating current) and to store and release energy from its magnetic field.
Leaded and SMT EMI Filters
Leaded and SMT EMI filters
are board-level solutions for EMI issues that require more filtering ability than the simpler ferrite bead or 3-terminal cap solutions might offer. These filters are a bit more complex, and are typically constructed with a combination of capacitance and inductance, capacitance and resistance, capacitance and varistor protection, capacitance and ferrite beads, or some other combination of these elements. These devices make for effective filtering in circuits where a good ground is available, as these filters drive the noise to ground. These EMI filters are used for general signal line filtering, as well as DC power line filtering.
(sometimes called clock oscillator or crystal oscillator) is a type of timing device that uses a quartz crystal element. Oscillators tend to be most expensive (typically) of the different timing devices; however, they provide the utmost in accuracy and flexibility. Very high frequency applications typically require an oscillator for timing, as might microprocessor (MPU) or digital signal processor (DSP) applications.
is a type of variable resistor; variable resistors are used where voltage and current variations are expected.
Potentiometers are comprised of a resistive element, a metal wiper blade, and a rotating shaft. When the shaft is rotated, the attached wiper blade moves along the resistive element. As the wiper moves, the resistance is increased or decreased. Potentiometers are usually externally mounted on electronic equipment, are frequently adjusted and are able to withstand more power than trimmers.
are also used in electronic circuits to control current flow through the circuit. Resistors control current by opposing the passage of electric current by incorporating resistive materials. All variable and fixed resistors can be grouped into one of three general basic types: carbon, film and wirewound. Depositing carbon in film form onto a ceramic core creates carbon resistors. Film resistors are composed of a resistive film deposited on, or inside of, an insulating cylinder or filament. Wirewound resistors are made up of resistance wire, which is wound around an insulated form.