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Off-the-shelf inductor, transformer and choke finder

Find the standard part first

Enter what the component has to meet. If a standard inductor, transformer or common mode choke already does, you get the part and where to buy it. If the nearest ones only come close, the value that is off is marked. Everything comes back in one table you can sort and trim, so you can decide whether close is close enough or whether the part should be designed.

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Component

Which kind of component are you looking for
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What it has to meet

Only the values that define the part. Resistance, size and the rest come back as columns you can sort and trim. Mark each value strict or flexible: a strict one also lists parts that miss it by up to 5 percent, a flexible one widens that to 30. A part that misses is never shown as a match, only as close, with the value marked.

Pick a component above and the values for it appear here.

No account, and no email unless you ask for the table by email. The values you search on are kept, without anything that identifies you, so we can see what the catalogue does not cover.

Before you buy

A match on the datasheet is not a match in the converter.

The finder compares catalogue values. Most of those are quoted at zero DC bias, 25 degrees C and a small signal, and your converter runs at none of those. Read the conditions, not the number, and if you would like a second pair of eyes on a part before you commit to it, send us the part number and your operating point.

The method

How the finder works

You enter only the values that define the part. The finder searches the DigiKey catalogue for power inductors, transformers and common mode chokes, and returns every part that meets them, and the ones that come close, in a single table with price and stock at each distributor. No account, and no email unless you ask for the table by email.

The values for each component

  • Power inductor: inductance, saturation current, RMS current and, if it matters, the switching frequency. The finder checks that against the self-resonant frequency of each part.
  • Transformer: the topology (flyback, forward, push-pull, isolated buck, resonant, LED driver, PoE, gate drive or current sense), primary inductance, turns ratio, power and switching frequency.
  • Common mode choke: the number of lines, rated current, and the common mode inductance or the impedance at 100 MHz.

Strict or flexible

Each value can be strict or flexible. A strict value also lists parts that miss it by up to 5 %, and a flexible one widens that to 30 %. A part that misses a value is never shown as a match, only as close, with the value that misses marked. DC resistance, size, maximum temperature and mounting come back as columns you can sort and trim.

Read the conditions, not the number

Catalogue values are measured under conditions that are rarely the ones in your converter, and they are not measured the same way by every manufacturer. Before you compare two parts, check:

  • Saturation current. Manufacturers define it at different inductance drops, commonly 10 %, 20 % or 30 % below the zero-current value. Two parts with the same Isat on the datasheet can behave very differently at your peak current.
  • RMS current. It is usually the current that raises the temperature by 20 K or 40 K in still air, depending on the manufacturer, and it does not include the core loss caused by your ripple.
  • Inductance. It is measured at a small signal, at a test frequency such as 100 kHz, and at about 25 °C. Your operating point has DC bias, a large AC flux swing and a higher temperature.
  • Transformer isolation. A test voltage is not an insulation class. Check whether the part is rated for functional, basic or reinforced insulation, and at which working voltage.
  • Common mode chokes. The impedance at 100 MHz says little about the band where your conducted emissions fail. Look at the full impedance curve.

When a standard part is not enough

In the first iterations of a project, a catalogue part is often the fastest way to test the converter. When nothing in the table holds at your real operating point, or the closest part is too large, too hot or close to end of life, send the same values to us as a custom specification from this page. We aim to answer within 24 hours.

Straight answers

Component finder, the usual questions.

Is the finder free?
Yes. There is no account, and no email unless you ask for the table to be sent to you. The values you search on are kept without anything that identifies you, so we can see which parts the catalogue does not cover.
Which distributors does it search?
It finds the parts in the DigiKey catalogue and adds price and stock from Mouser, Arrow and Farnell, which is Newark in the United States. Prices are shown in EUR for Europe or in USD for the United States, with the stock at each distributor.
What is the difference between strict and flexible?
A strict value also shows parts that miss it by up to 5 %. A flexible value widens that to 30 %. A part that misses is always shown as close, never as a match, with the value that misses marked.
Why does a part that matches the datasheet fail in my converter?
Because catalogue values are measured at zero DC bias, about 25 °C and a small signal, and each manufacturer defines saturation and rated current in its own way. Your converter runs with DC bias, ripple and a higher temperature. Check the curves at your operating point before you commit to a part.
Can I search for a replacement for an obsolete part?
Yes. Enter the values that define the old part and the finder returns the standard parts that meet them. If none does, we can design a form, fit and function replacement. See compatible magnetics.
What if no standard part fits?
Send the same values as a custom specification from this page. We design the part for your real operating point and build it from one unit, with no minimum order.

Send us your spec