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P
Phil Hobbs
Guest
On 2020-07-15 19:25, John Larkin wrote:
Yup. But there are a lot, a lot of good uses for a BFS17 equivalent
with a beta of 500, no Early effect to speak of, and 0.3 nV 1-Hz noise
in the flatband. Especially at 17 cents in reels.
Not at 100 MHz. The peak goes much higher--the Murata BLM1xBB beads are
pretty amazing actually.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
On Wed, 15 Jul 2020 18:43:26 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2020-07-15 15:38, Simon S Aysdie wrote:
On Tuesday, July 14, 2020 at 6:01:54 AM UTC-7, Phil Hobbs wrote:
So I was chatting with my local Mini Circuits rep, who also
handles Gowanda. He asked if I was interested in conical
inductors, which I certainly am, and how much I wanted to pay for
them.
Remembering that JL had said that the Coilcraft patent had expired,
I said \"forty cents in reels\".
Turns out that Gowanda won\'t go below $10 apiece in reels. I
pointed out that I mostly wanted to use it with BFP640s and really
wasn\'t going to use a $10 inductor to decouple a 20-cent
transistor--especially since I can use series-connected
0201/0402/0603 inductors and beads to do almost as good a job, for
$0.12 total.
Those things are just ordinary ferrite or powdered iron, wound
with ordinary copper, and can\'t be that hard to make, so once the
patent(s) expire, it\'s hard to imagine how they can maintain that
pricing level.
What gives, do you suppose?
I suppose they are harder to make than we\'d like, although I don\'t
know why..
I have used Gowanda and Piconics. Yep--still pricy even though the
patents are out.
My latest idea is to emulate a conical with a series of 2-4 \"stepped
sizes\" of CCI ferrite core 0201,0402, 0603 inductors. I haven\'t had
time to develop a library of \"favorite combinations.\" Some people are
hesitant to use these coils above the first self resonance, but it is
fine to do so.
Yup, that\'s my trick too. Starting with the 0402 they\'re actually beads
(Murata BLM15BA/BLM18BB). That helps control the effects of the pads in
between the beads. I haven\'t spent enough time on it to optimize them,
but they\'re pretty good medicine.
For stabilizing BFP640s, I like to use a single BLM15BB050SN1 in the
base. Works like the bomb--I mostly use them for their studly beta,
Early voltage, and low noise--the Infineon model has BF=450, VAF=1000,
and RB=3 ohms, and the 1/f noise corner is pretty low considering it\'s a
40-GHz transistor.
Cheers
Phil Hobbs
The Murata datasheet is 277 pages long!
Surely a bead in the base kills Ft, which is why it\'s there. But does
it also add HF noise? Seems like it would.
Yup. But there are a lot, a lot of good uses for a BFS17 equivalent
with a beta of 500, no Early effect to speak of, and 0.3 nV 1-Hz noise
in the flatband. Especially at 17 cents in reels.
I guess a 5 ohm bead is no big deal.
Not at 100 MHz. The peak goes much higher--the Murata BLM1xBB beads are
pretty amazing actually.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com