Air Core Coil

The term “air core coil” describes an inductor that does not use a magnetic core made of a ferromagnetic material. The coils are wound on plastic, ceramic, or other nonmagnetic forms, as well as those that actually have air inside the windings.

Air Core Coils are inductive components without a ferromagnetic core and therefore have relatively low inductance. They are often used at high frequencies because they are free from energy losses that occur in ferromagnetic cores, which increase with frequency.

  • The inductance is not affected by the current it carries.
  • Air Coils are 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.
  • Inductance of the coil may change due to mechanical vibrations because the coil is not rigidly supported by a coil form.
  • 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 SRF, and higher copper loss.

Bobbin Wound Inductors

Bobbin wound inductors refers to a type or method of construction of winding inductors chokes and reactors. Toroidal coils are wound directly onto a toroidal core. The core may be coated or boxed to insulate it from the coil windings. In contrast, bobbin wound inductor coils are wound independently of the core. The coil must hold its shape or form until the coil is assembled onto the inductor core. One common method of doing this is to wind the coil onto a bobbin (also referred to as a spool), hence the term “bobbin wound winding inductor”.

The bobbin is a pre-formed reasonably rigid part. The bobbin material is usually (but not always) an insulating material, hence it can provide electrical isolation between the coil and the adjoining core material provided suitable creepage distance is used. Multi-section bobbins are available to provide increased electrical isolation between coil windings.

Bobbin wound inductors are used in a variety of applications, hence bobbins are made from a variety of materials: plastics, phenolic, glass, TeflonTM and others. Most bobbins are molded. Some are fabricated. Bobbin designs for bobbin wound inductors often provide terminals, pins, and/or surface mount pads to ease wire termination and to facilitate printed circuit board mounting.

  • Mountings can include pin-through, surface mount, or chassis mount.
  • Toroidal inductors are usually preferred when high efficiency and optimum performance are desired. Tube based construction tends to be more customized hence a variety of inductor shapes are possible.

Bobbin winding inductors (and transformers) are available in a variety of shapes. Bobbin wound inductor shapes include pot cores (round), “RM” (square pot cores), “RS” (round slab pot cores) and “DS” (double slab pot cores), “EP”, “PQ”, “E”, “EI”, “EEM”, “EFD”, “U”, “UI”, “EC”, “ETD”, “ER”, “EER”, and some others including custom shapes. Bobbin wound inductors in these shapes are available in several different sizes.

Bobbin wound inductors (and transformers) can also use a variety of core materials: laminated or taped wound silicon steel alloys, nickel-iron alloys, cobalt alloys; powdered irons and nickels; ferrite; air core; core materials processed for square loop or round loop properties; and others.

Chip Inductors

Yes, but unlike other chip manufacturers, Gowanda’s chip inductors utilize co-fired terminations and fully encapsulated designs to address the market need for:

  • Chemical Resistance
  • Vibration/sheer resistance
  • Electrical and mechanical integrity
  • Durability during handling/processing
  • Implantable device components (human body)

View more information here.

Conical Inductors

YES! Our conicals are specifically designed for high frequency applications where ultra-low insertion loss & return loss are design requirements. Their unique construction helps to limit the effects caused by stray capacitance. Reliability to M83446D, upscreening capability to MIL-STD-981, unique footprints and both standard and custom design options enhance utility.

For more information click here.

Date Code / Lot Code

Date and Lot Codes are represented in YYWWL format – Year/Week/Lot Symbol.

Dash Numbers

The dash number is a three-digit code, represented as XXX within Dimensional Specification files & Datasheet drawings, that corresponds to the three numbers that follow the series name in the part number.

– 100 = 0.1 µH
– 101 = 1.0 µH
– 102 = 10 µH
– 103 = 100 µH


Types include bobbin wound inductors, toroidal inductors, air core (no core), tube wound, foil wound, wound with litz wire, encapsulated (potted), laminated, powdered core, and others. An Inductor’s core material is heavily influenced by the application’s frequency range. Line frequency applications usually use a laminated or tape wound silicon steel core stack.

Lead-Free / RoHS

Almost all of our parts are RoHS compliant, but not necessarily lead free. Any lead present in our RoHS-compliant parts is within allowed limits or is explicitly exempt in the RoHS directive.

Add “LF” suffix to the end of a part number for RoHS requirement.

Example: SML32S-101KLF, Gowanda designates a component RoHS-compliant by adding “LF” (lead free) to the part number. These LF components meet the ≤ 0.10% lead requirement and they are compatible with 260°C soldering processes.

Note: this applies as only to series/part numbers that are marked as RoHS compliant.

Medical, Military, and Aerospace Qualified

Yes. You can find all information pertaining to our Medical, Military/Aero or Space applications on our industry pages.

Non-Magnetic Products

Yes, Gowanda offers both Surface Mount and Thru-Hole Non-Magnetic Inductors. You can find more information about these series on our Non-Magnetic Inductor page.

  • Designs utilize non-magnetic materials to avoid problems in magnetic-sensitive applications
  • Suitable for medical applications such as MRI equipment where magnetic materials would compromise system performance
  • Gowanda was the first inductor manufacturer to attain ISO 13845, establishing it as a leader in this field
  • RF surface mount and RF thru-hole designs offer versatility to design engineers
  • Available in application-specific designs
  • These inductors provide relative permeability of ≤ 1.00003

Obsolete/Discontinued Parts

Please contact us regarding the part you are unable to find in case there is an error at our website. Although it happens very rarely, from time to time there are forces outside of our control that result in a particular part being discontinued; if that’s the case we may be able to suggest an alternate part to suit your needs.

Outgassing Test

Yes, Gowanda tests per ASTM E595.

If a Gowanda series is marked with “Outgassing Tested per ASTM E595” this means that this series meets a TML (Total Mass Loss) requirement of 1.0% maximum when tested in accordance with ASTM E595; this calculation does not include WVR (Water Vapor Recovered).

Request a Quote

There are two (2) methods of submitting an RFQ form on this site:

  1. By adding products to your cart and then filling in the subsequent form on the checkout page and submitting. This should be used if you have found and added to your cart the discreet part numbers utilized at Gowanda.
  2. By visiting our Request for Quote page. This page is unique in that it will pull in the URL of the last page that you have visited to give our team here an idea of what it is you are looking for. Like the other path to submitting an RFQ, the user must complete the form and submit for it to be sent to our team here at Gowanda.

If you need further assistance with either option, please feel free to Contact Us!

We typically reply to RFQ submissions within two business days. Please call us if you require immediate assistance.

Selecting the Best Part

Yes, our search parameters that are on each product page will help you narrow down the results of what we offer as Standard Product. If you do not find your exact specification, you can submit a form to our Engineering team.

You can also use our search metrics to search by competitor part numbers.

Many of our transformers can be adapted to a variety of circuit uses, by considering different connections for the windings. There are, however, many variables to consider when adapting a component designed for one application for use in a different application.

Switch Mode Power Transformer

Switch mode power transformers (and supplies) get their name from the switching action needed to sustain transformer operation. By controlling the amount of on time and off time of the switches, one can also control the amount of power delivered to the transformers load (or load circuit). The voltage can be fed to the switch mode power transformer in voltage pulses. The pulse duration is a portion of an overall cycle time. The cycle time is equal to the inverse of the operating frequency. The terms duty cycle and pulse width modulation arise from the control of the switching on time and off time.

Switch mode power transformers are used extensively in electronic applications, usually within a switch mode power supply. A switch mode power supply is usually powered from a DC source, such as a battery. The switching mode power supply converts the input DC source to one or more output DC sources. The power supplies are often referred to as DC to DC converters. In similar fashion, the switch mode power transformers are often referred to as DC to DC transformers (or DC-DC transformers). A switch mode power transformer can have several secondary windings. Consequently, the switch mode transformer permits multiple outputs which can be electrically isolated from one another. Transformer action permits one to step up or step down the voltage as needed via an appropriate turns ratio. Pulse width modulation is used to provide voltage regulation.

Many electronic applications require some sort of power supply which converts power from the conventional low frequency sinusoidal AC wall socket (for example, 115V 60 Hz) to the necessary voltage, current, and/or waveform required by the circuit. Typically the circuits need a well-regulated DC voltage. Designers often choose either a rectifier type circuit (to convert AC voltage to DC voltage), a switch mode power supply, or both. The AC voltage is first rectified to provide a DC voltage. The DC voltage varies as the AC voltage varies, hence good voltage regulation cannot be assured. One or more switching mode power supplies follow the rectifying circuitry. The switching mode power supplies provide a more tightly regulated output voltage. AC rectification is not a necessity. Although tricky, it is possible, through switching actions, to divide (chop) the AC waveform into a series of pulses, which are directly fed into the switching mode power transformer. Pulse width modulation is used to control the regulation.

The design of a switch mode power transformer will differ depending upon the type of circuit used. There are many variations of switching mode power supplies, but they can be narrowed down to three basic circuit configurations (each also has a mirrored configuration); Buck, Boost, and Flyback. Be aware that the name for the Buck circuit varies from industry to industry and from person to person. It may also be referred to as an inverter, DC converter, forward converter, feed forward, and others. There are also unipolar and bipolar (push-pull) versions.

For additional information please refer to Gowanda’s Switch Mode Power Transformer Theory page.

Power transformers and inductors are essentially AC (alternating current) devices. They cannot sustain transformer operation from a fixed D.C. (direct current) voltage source. However, they can sustain transformer operation in a transient condition(s) that allows resetting or reversal of the transformer’s magnetic flux levels. An AC voltage source keeps reversing the polarity of the voltage being applied across the transformer. Consequently, the magnetic fields keeps reversing. Voltage reversal can also be accomplished with a D.C. source such as a battery. The connections between the D.C. source and the transformers are repeatedly switched, thereby reversing the voltage polarity across the transformer, hence reversing the magnetic field. The transformer can also be switched off from the D.C. source. In this case the magnetic field simply collapses until it reaches its residual value (ideally equal to zero). This collapse resets the transformer’s magnetic field.

T-Level Product

T-Level product is used for high reliability critical military applications.

T-Level product is 100% tested in accordance with MIL-PRF-27 Group A Subgroup 1 which includes:

  • Thermal Shock
  • Burn In
  • Radiographic Inspection Tests

Tape and Reel

Tape and reel information is included on each series datasheet and on each product page on the website. ALL series packaging information can be found on the Packaging Specifications webpage.

Toroidal Transformers

Any electronic transformer application that can accommodate the shape of a toroidal transformer can use one. Although usable, toroidal transformers are not always practical for some applications.

Materials available include silicon steel, nickel iron, moly-permalloy powder, iron powdered, amorphous, ferrites, and others. Silicon steel and nickel iron are available as tape wound cores or laminated pieces.

A 360 degree wound toroidal transformer has a high degree of symmetry because of its circular shape. This leads to near complete magnetic field cancellation outside of its coil, hence the toroidal transformer has less leakage inductance and less EMI when compared against other transformers of equal power rating.

Toroidal transformers with a round core cross section are better performers than toroidal transformers with a rectangular cross section. The cancellation is more complete for the round cross section. The round cross section also gives a shorter turn length per unit of cross sectional area, hence lower winding resistances. The toroidal transformer also has better winding to winding magnetic coupling because of its toroidal shape. The coupling is dependent on the winding being wound a full 360 degrees around the core and wound directly over the prior winding, hence sector wound windings do not couple as well and have higher leakage inductance. As winding turns are positioned further away from the core less complete coupling will occur; hence toroidal transformers with multi-layered windings will exhibit more leakage inductance.

Gapped toroidal transformers usually require that the gap be filled with some type of insulating material to facilitate the winding process. This is an extra expense. Split core current transformers can be assembled directly on a conductor while toroids must be passed over a disconnected end of the conductor. A toroid can be split in two, but a suitable clamping mechanism (difficult and costly) is required. Some printed circuit boards are space critical. Mounting a toroidal transformer flat on the board may take up too much precious board area. Some applications also have restricted height so the toroid cannot be mounted vertically.

Sufficient winding wire must first be wound (loaded) onto the winding shuttle, then wound onto the toroidal transformer’s core. After that, the best situation, from a cost perspective, is if no insulation is required over the winding and the next winding uses the same wire size. If the wire is different, then the leftover wire must be removed and the wire for the next winding must be loaded. However, if the winding must be insulated, then it must either be insulated (taped) by hand or the toroidal transformer must be removed and taken to a separate taping machine, then placed back on the toroid winding machine after taping. The shuttle must then be loaded with the wire size and type for the toroidal transformer’s next winding. A toroidal transformer with a single winding (auto-transformer, current transformer) wound on a coated core will probably be cost competitive with an equivalent bobbin or tube wound transformer since the toroidal transformer will not require a bobbin or tube. The cost differential will then depend on the method and cost of mounting the transformers.


The weight of a Gowanda part is typically specified on the data sheet for the part. In the case of a part series, a weight range may be given that covers the entire series.