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Path: ...!weretis.net!feeder8.news.weretis.net!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: Thu, 5 Sep 2024 22:44:36 -0000 (UTC) Organization: A noiseless patient Spider Lines: 120 Message-ID: <vbdc8j$gsdh$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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Fri, 06 Sep 2024 00:44:36 +0200 (CEST) Injection-Info: dont-email.me; posting-host="8a0662926ce6fca6bf49ec0d1e8c3786"; logging-data="553393"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+8NUFhR7b5iQzUNV7esPqe" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:vUuMnQQfUnSuSW56+YNLkukCuxc= sha1:KyW1tIHmMx7oSNUs8+byYdeM4CA= Bytes: 5706 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