RF bipolars RIP

Looks like NXP is discontinuing their SOT89 RF bipolars, like BFQ149 and BFG31 and such. Bummer. I just designed them in.

They have equivalent SOT23s that they rate for 600 milliwatts.

SIX HUNDRED MILLIWATTS!

Maybe I can get by with some OnSemi 600 MHz SOT89 parts. Kinda slow.

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John Larkin         Highland Technology, Inc 
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John Larkin
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Lifetime buys in order.

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 Thanks, 
    - Win
Reply to
Winfield Hill

Infineon stil has Sot-89 RF NPNs, but the PNP Situation is ugly. No more easy current source loads at RF.

cheers, Gerhard

Reply to
Gerhard Hoffmann

Yeah, I just designed in a SOT89 PNP, BFQ149.

Maybe I'll buy 5000 and worry about it later.

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John Larkin         Highland Technology, Inc 
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Reply to
John Larkin

What about Diodes / Zetex parts?

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    - Win
Reply to
Winfield Hill

Maybe you'll be dead...:^) or maybe someone else will pick-em up? I think we're still buying RF power transistors from Russia or somewhere... ~70 MHz at 1-2W. (70 MHz is my freq, I don't recall where they roll off.)

Can't you use a Fet somehow? George H.

Reply to
George Herold

What's the good NPN complement?

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Reply to
Winfield Hill

BFQ18, still listed as in production.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

I spent the afternoon looking. All the available SOT89s are really slow. I need to dissipate 600 mW in the PNP, so the SOT23 and such are out.

Same issue as the phemts: fast discretes are disappearing.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

So one would have to parallel BFT93s, then. Blech.

I ordered a reel of BFG403s (basically a 17-GHz BFT25A), which are on LTB, and am plotting to get some SKY65050s, ATF38143s, ATF55143s, BFP640s, BFP650s, BFU520As, and a few others that are still apparently in production. Ties up a few $k in inventory, but preserves freedom of action and possibly future competitive advantage.

Inconvenient.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Phil Hobbs

Or maybe buy 20k, at less than $0.50/ea that could be a nice investment if you end up not using them. It is likely that obsolete parts dealers come banging on your door who are then willing to pay 5-10x that money. I just had a situation like that but could not help them because I didn't know any former clients who had stock in the part left.

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Regards, Joerg 

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Reply to
Joerg

Yes. And balance the currents. And pray they don't oscillate.

It's rude of people to not make p-channel phemts.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

One approach when you don't need wide range fast slewing is an NPN connected as a pseudo-inductor (resistor from C-B, cap from B-E). It's good for stiffening PNP current sources. Of course the limited slew range probably leaves out every single one of your applications. :(

Tubes have a similar problem, for similar reasons. ;)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

OK, you can stop right there!

is an NPN

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

However, tubes have a staunch constituency and the Russians and Chinese have figured out how to cash in.

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Even very cool looking ones:

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I had a bet going with a boss in the 80's that our ultrasound Doppler units could have already been built very economically in WW-II and before, with tubes. He didn't believe it. When I gradually retire I could build such a machine. Got the tubes, sockets and stuff. Problem is, neither of us has cardiovascular issues so we don't really need it. Also, the only way to build such a device would be with highly polished wood and brass as an enclosure.

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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

I don't think they've figured out how to make P-channel ones yet, though. ;)

When I was at IBM, I used an 811A to switch bias onto the grids of a drift chamber. No semiconductor could come near its performance for that job.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Perhaps we should compile a list of classic endangered discretes between us so we can stock up on 'em while we can. Not that it'll do the designers much good, but repairers and whatnot could benefit.

Reply to
Cursitor Doom

Yes, the Russians make some killer tubes, god bless 'em and good luck to them for their efforts. Not sure about Chinese ones, though. I still don't trust anything made in China.

Reply to
Cursitor Doom

Some electronics from China are of good quality. Some of the dealers there are less than honest though. I just had one who promised twice to send a warranty replacement, never did, and doesn't respond to emails. I'll have to check how long one can place a credit card payment in dispute, just out of principle.

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Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Black wrinkle finish, engraved and filled lettering.

Geez, there was some ugly gear back when. The Tek 530-series scopes were a stunning style breakthrough.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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John Larkin

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