Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
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: Sun, 8 Sep 2024 00:16:59 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 125
Message-ID: <vbiqdr$1k5m8$1@dont-email.me>
References: <6b1217f0-f55b-95b4-6516-6914d18d0e91@electrooptical.net>
 <vbbia5$25sla$1@solani.org>
 <vbbmn9$8mib$1@dont-email.me>
 <j2fjdjhn1e4uht19jlundnl45mtanlsghq@4ax.com>
 <60cd9dfe-42b7-8d6c-d101-8e771bc762e8@electrooptical.net>
 <7oakdjl3maqislrtoba0lunseakhroo22o@4ax.com>
 <NHknlWwLIQIumCNTcOxTkFklwQHMrNgK@bonus.frugalusenet.com>
 <vbipiq$1k0jo$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 08 Sep 2024 02:16:59 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="3fadb2c785c49cea2f9d2eba7db44ec0";
	logging-data="1709768"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/0NbvZH5qp5ysc3U22atOB"
User-Agent: NewsTap/5.5 (iPhone/iPod Touch)
Cancel-Lock: sha1:m1mGHeeT/uaQB6truxE+GNx9w+g=
	sha1:vO6jesy60Fyyr4rQ5Klw+PIG8Dg=
Bytes: 5976

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
> bitrex <user@example.net> wrote:
>> On 9/5/2024 6:06 PM, john larkin 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.  It’s not a 50-ohm system, so using those would be hard. I have
>>>>>> thousands  for personal use, but can’t put them in licensed designs, which
>>>>>> is what I’m 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?
>>> 
>> 
>> What about a PFET/JEFT cascode buffer kinda like:
>> 
>> <https://imgur.com/a/5fBR8Gb>
>> 
> 
> There aren’t any decent discrete pfets left, and there never was a 5 GHz
> one. 

I should add that a partially integrated solution could probably do a good
job at this. 

The NFET has many performance constraints that might be hard to reproduce
on-chip, but the following stages are more flexible. 

Cheers 

Phil Hobbs 


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