Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them.

From	Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups	sci.electronics.design
Subject	Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them.
Date	2024-09-05 22:44 +0000
Organization	A noiseless patient Spider
Message-ID	<vbdc8j$gsdh$1@dont-email.me> (permalink)
References	(1 earlier) <vbbia5$25sla$1@solani.org> <vbbmn9$8mib$1@dont-email.me> <j2fjdjhn1e4uht19jlundnl45mtanlsghq@4ax.com> <60cd9dfe-42b7-8d6c-d101-8e771bc762e8@electrooptical.net> <7oakdjl3maqislrtoba0lunseakhroo22o@4ax.com>

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john larkin <jl@650pot.com> wrote:
> On Thu, 5 Sep 2024 10:49:42 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
>> On 2024-09-05 10:14, john larkin wrote:
>>> On Thu, 5 Sep 2024 07:30:50 -0000 (UTC), Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>> 
>>>> Jan Panteltje <alien@comet.invalid> wrote:
>>>>> On a sunny day (Wed, 4 Sep 2024 17:54:19 -0400) it happened Phil Hobbs
>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote in
>>>>> <6b1217f0-f55b-95b4-6516-6914d18d0e91@electrooptical.net>:
>>>>> 
>>>>>> The NTE2403, similar to the BFT92, but a bit better overall.  Dunno who
>>>>>> actually made them. (I saw the news on s.e.repair today.)
>>>>>> 
>>>>>> Rochester claims to have 1,500,000 of the 2SA1462 (1.8 GHz) for 20
>>>>>> cents, but that's all she wrote.
>>>>>> 
>>>>>> I have a couple of reels of BFT92s and one of BFG31s, so I'm good for
>>>>>> protos and small production, but I can't use PNP wraparound bootstraps
>>>>>> for customer designs anymore. :(
>>>>>> 
>>>>>> Barstids.
>>>>>> 
>>>>>> Cheers
>>>>>> 
>>>>>> Phil Hobbs
>>>>> 
>>>>> Lots if RF snall signal low noise stoff in LNBs:
>>>>> https://www.infineon.com/dgdl/Infineon-Design_guide_for_RF-transistors_and_diode_in_Low-Noise-Block-ApplicationNotes-v01_00-EN.pdf?fileId=8ac78c8c7e7124d1017f01f071aa5b8f
>>>>> Does that help?
>>>>> 
>>>>> 
>>>>> Complete LNBs inclusive transistors and peeseebees are 5 dollies on ebay.
>>>>> 
>>>>> 
>>>> 
>>>> Thanks.  Its not a 50-ohm system, so using those would be hard. I have
>>>> thousands  for personal use, but cant put them in licensed designs, which
>>>> is what Im moaning about.
>>>> 
>>>> Cheers
>>>> 
>>>> Phil Hobbs
>>> 
>>> Can you use mmics? There are some really cool, fast, cheap, low-noise
>>> things around. Just because the RF boys test everything at 50 ohms
>>> doesn't mean we have to use them at 50 ohms.
>>> 
>> 
>> For the wraparound topology, which is the second-best follower I know of,
>> 
>> VDD 0------*---------*
>> |         |
>> R         |
>> R         |
>> R         /
>> |       |V
>> *-------|  BFT92
>> |       |\
>> |--*         \
>> In  0-->|  CPH3910   |
>> |--*         |
>> |         |
>> |         |
>> *---------*----0   Follower output
>> |
>> V (tail current source)
>> 
>> the BJT needs to be a PNP.
>> 
>> It's a nice circuit, because the PNP reduces the output impedance a lot 
>> without adding much noise at all--way better than an NPN follower after 
>> the FET.
>> 
>> Because of the local feedback, the transistors need to be fairly 
>> different in speed to maintain stability.  The FET is about a 750-MHz 
>> device, so a 5-GHz PNP is great.  The alternative would be a 100-MHz 
>> PNP, which would be too depressing to contemplate. :(
>> 
>> The very best follower topology I know about is a fancy bootstrapped 
>> version of the White cathode follower, where the feedback is applied via 
>> the tail source.  That's much harder to stabilize, because there are 
>> three transistors in the local feedback loop, but on the other hand its 
>> gain is 0.9997 at baseband and above 0.995 at 10 MHz.  (You can't 
>> readily measure those sorts of numbers directly, so I inferred them from 
>> its performance as a bootstrap.)
>> 
>> The reason I care about getting such accurate bootstraps is a bit 
>> subtle--probably I'd have enough bandwidth improvement with a gain of 
>> 0.9, but that extra 10% shows up as a gnarly settling transient at late 
>> times, which screws up measurements.  0.9997 is dramatically better.
>> 
>> Cheers
>> 
>> Phil Hobbs
> 
> The CPH3910 is a jfet. Might an un-assisted PHEMT be better?
> 
> 

I’ve used them a fair amount in front ends, generally with a SiGe NPN
cascode-slash-drain bootstrap.  Their transconductance is a few times
higher than a CPH3910’s, but not as good as the local-feedback circuit’s. 

pHEMTs have very low drain impedance—the late lamented ATF38143 had a
voltage gain of ~0.7 as a follower, even with a current sink in the tail.  

Their amazing noise floor (~0.3 nV in 1 Hz) makes them well worth patching
up, but they do take some patching. 

Cheers 

Phil Hobbs 


-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics

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Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-04 17:54 -0400
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. john larkin <jlarkin_highland_tech> - 2024-09-04 19:50 -0700
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 07:22 +0000
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Jan Panteltje <alien@comet.invalid> - 2024-09-05 06:15 +0000
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 07:30 +0000
      Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. john larkin <jlarkin_highland_tech> - 2024-09-05 07:14 -0700
        Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 10:49 -0400
          Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. john larkin <jl@650pot.com> - 2024-09-05 15:06 -0700
            Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 22:44 +0000
              Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. john larkin <jl@650pot.com> - 2024-09-05 15:55 -0700
                Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-06 00:07 +0000
                Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Jan Panteltje <alien@comet.invalid> - 2024-09-06 06:44 +0000
            Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. bitrex <user@example.net> - 2024-09-07 23:40 +0000
              Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-08 00:02 +0000
                Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-08 00:16 +0000
          Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Gerhard Hoffmann <dk4xp@arcor.de> - 2024-09-06 01:43 +0200
            Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. john larkin <jl@650pot.com> - 2024-09-05 16:58 -0700
            Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-06 00:13 +0000
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Bill Sloman <bill.sloman@ieee.org> - 2024-09-05 21:15 +1000
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. bitrex <user@example.net> - 2024-09-05 14:24 +0000
      Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 18:17 +0000
        Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Gerhard Hoffmann <dk4xp@arcor.de> - 2024-09-05 20:57 +0200
          Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-05 19:58 +0000
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Chris Jones <lugnut808@spam.yahoo.com> - 2024-09-06 22:47 +1000
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Gerhard Hoffmann <dk4xp@arcor.de> - 2024-09-06 17:31 +0200
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-06 13:33 -0400
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Joerg <news@analogconsultants.com> - 2024-09-06 15:59 -0700
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-07 21:46 +0000
      Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Joerg <news@analogconsultants.com> - 2024-09-09 14:02 -0700
  Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-09 21:59 -0400
    Re: Drat. NTE is gone, and they took the last 5-GHz PNP with them. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2024-09-09 22:12 -0400

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