what is 300R on an inductor?

Did you measure the resistance of this 'inductor' ?

peter

Its on a schematic and I don't have access to the circuit. It is drawn as an inductor and not a resistor. The value is associated with the lines going to the power leads of a USB connector (the +%VDC and the Gnd lines).

Dave

as

Typical USB power chokes may not specify an inductance at all, but instead specify impedance at 100MHz. 300 Ohms at 100MHz is entirely typical. Invariably it's a common mode choke.

This specification trend for Z@100MHz seems to be common for ferrite beads too.

Tim.

Typical USB power chokes may not specify an inductance at all, but instead specify impedance at 100MHz. 300 Ohms at 100MHz is entirely typical. Invariably it's a common mode choke.

This specification trend for Z@100MHz seems to be common for ferrite beads too.

Tim.

Thanks

-- Dave

Ferrite beads look more like resistors than inductors at their design frequency.

On Mon, 19 Jan 2009 11:16:06 -0700, "starfire" put finger to keyboard and composed:

Here are a few examples:

An inductor marked "1R2" has an inductance of 1.2uH at 100kHz. An inductor marked "220" has an inductance of 22.0uH.

Maybe the dimensions, DC resistance, and application could provide some confirmation.

- Franc Zabkar