Path: ...!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Cursitor Doom <cd@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: Interesting inductor
Date: Wed, 13 Mar 2024 22:53:42 +0000
Organization: A noiseless patient Spider
Lines: 33
Message-ID: <5fb4vidh7pv9io2uuhnghco8cma464pgoe@4ax.com>
References: <f6aba241-3e20-db1f-36ea-8641ca6fac49@electrooptical.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Info: dont-email.me; posting-host="f2aa05fec5f688c326abb99b0acb2e4e";
	logging-data="1262541"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19IZoIq1Flko8GfvlO/QV1uYiLD5rc9nEE="
User-Agent: ForteAgent/8.00.32.1272
Cancel-Lock: sha1:oMthJcxR9L1ExbOs4ehKDfaqX0k=
Bytes: 2203

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