Re: Interesting inductor

On Tue, 12 Mar 2024 23:17:57 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

So I'm doing a new lab amp product.
Our existing one is 500 Hz -- 20 MHz, 1.1 nV/sqrt(Hz).
>
The new one is aiming to be 10 kHz -- 200 MHz, 0.25 nV/sqrt(Hz).  The
spherical cows love it, so we'll see when the test boards arrive later
this week.
>
As part of the design, I wanted to make an emitter follower with a
decent amount of inductance in series with its tail resistor, to avoid
the transistor turning off on fast negative edges and causing linearity
problems.
>
Searching on Digikey, I found this very interesting part:
<https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B82498F1472J000/697521>.
>
4.7 uH 0805 wirewound, with a self-resonant frequency of _210 MHz_,
which is several times higher than many other parts of that description.
  That corresponds to an effective parallel capacitance of 0.12 pF,
about that of a resistor of the same size, despite all the copper windings.
>
Pretty nifty, if true.  (Parts on order.)

As you say, nifty. Do you have some means of verifying that Fo claim,
Phil? Even a NanoVNA would give a pretty good idea if it's really that
high.

>
Cheers
>
Phil Hobbs