J310 JFets - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: July 27, 2017, 03:35:58 pm
content: Arrgh, so, I find the J310 is a nice little VHF FET, decent package, rated by a lot of people who homebrew and is used in a *lot* of projects out there on the web.Except, it's obsolete in TO-92.So, do I bodge it into my homebrew projects in SMD form, search for some magical end of rainbow pot of J310s somewhere or is there a nice alternative out there that's cheap enough for me to buy a bag of 50 or more?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 27, 2017, 04:59:48 pm
content: THT case jfets are getting more an more obsolete and expensive, but there are SMD alternatives. If it is for RF application the tendency is anyway to go SMD and the SOT23 case is still possible dead bug style. One might be lucky and get a few old ones from not so suspicious sites, but they are generally already expensive - so not to buy like 50 pieces.The direct replacement would be MMBFJ310 or SST310.

author: CJay
author_rank: Super Contributor
timestamp: July 27, 2017, 05:46:40 pm
content: Most of what I will use them for won't extend beyond ~50MHz so I'm thinking SOT to TO-92 adapter board as it's looking incredibly unlikely I will find a trustworthy source of them (alibaba is full of them but, trusting they're the real deal, hmm...).An adapter board also opens up the possibility of making a single package cascode/dual gate FET which could be usefulThe SST310 is already showing as obsolete so I'm just about to order a hundred of the others.

author: medical-nerd
author_rank: Regular Contributor
timestamp: July 27, 2017, 06:02:32 pm
content: HiyaThere is some on ebay in uk:http://www.ebay.co.uk/itm/J310-N-Channel-RF-Amp-JFET-On-Tape-Lot-of-10-/172564131279?hash=item282d9fadcf:g:4BUAAOSwWxNYvVABBy seller PW-ELECTRONICSThey have sold a lot of these over the past couple of years - I may stock up.Cheers

author: Kleinstein
author_rank: Super Contributor
timestamp: July 27, 2017, 06:37:11 pm
content: I would not expect the SOT23 version to go obsolete to soon. There are several manufacturers for this - some may stop this or just do minute changes to the tapes.For the BF862 there was quite some confusion on going obsolete. However in this case they only changes the tapes (something like different positions / spacing. For manual use this does not matter and for the machines it is just entering the correct tape type.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 27, 2017, 08:52:00 pm
content: On Semi recently introduced a handful of new JFETs, even; they're very slightly better than the esteemed BF862.If you can't handle SOT-23 and such, man, Idunno. You're screwing yourself over if you let yourself think that.I find SMT better for everything except breadboarding -- and the solderless breadboard isn't of much use in applications like this (RF amps and such, up to 50MHz), so you're surely not losing much?And if you still need to breadboard, breakout boards are easily made -- I have a couple 2N7002 and BSS84 floating around, that are mounted on hunks of FR-4, carved up for the connections, with pigtails soldered on for breadboarding. Ugly but it works.Tim

author: LaserSteve
author_rank: Super Contributor
timestamp: July 27, 2017, 09:55:20 pm
content: Try a U310 ?Mouser has 234 in the plastic package.Not cheap at 7.34 each..They have J309 as well, and I'm having a hard time telling the difference from the Motorola / On Semi data sheet.J309 are 4.09$ each with 134 in stockSteve

author: cdev
author_rank: Super Contributor
timestamp: July 28, 2017, 05:08:37 am
content: Been meaning to get some too...

author: CJay
author_rank: Super Contributor
timestamp: July 28, 2017, 07:21:55 am
content: Quote from: LaserSteve on July 27, 2017, 09:55:20 pmHeh, I was about to post that I'd found a bag of J309s in my stash and was finding it difficult to spot the difference in the datasheet.I've gone the SOT-23 route for J310s, a strip of 100 should be appearing in the post today, they were ~18p each.

author: CJay
author_rank: Super Contributor
timestamp: July 28, 2017, 07:59:26 am
content: Quote from: T3sl4co1l on July 27, 2017, 08:52:00 pmInteresting, have you any part numbers for the new ones?Heh, I'm definitely not scared of SMT, I love how cheap I can find SMD versions of chips like the NE602, AD8307 etc.The main reason for an adapter board was just to make it simpler to throw one into a circuit that's already together without having to do too much alteration and of course I can make 'dual gate' modules (though, I've also got a bag of BF981 'dots') but I also have to admit I prefer a TO-92 (or non SMT), I don't really know why other than it 'feels' nicer which is a ridiculous reason, especially as I know how much more RF friendly SMD is.(An aside, before the internet I 'invented' manhattan and ugly construction techniques all by myself, of course *many* other constructors must have been doing it for many years already but I'd never seen it done, indeed the guys at the local electronics shops were impressed with how literal the technique was, one commented 'It's like you've soldered the circuit diagram to a board')

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 28, 2017, 08:59:30 am
content: Quote from: CJay on July 27, 2017, 03:35:58 pmIt is still available in TO-92.CheersAlex

author: bd139
author_rank: Super Contributor
timestamp: July 28, 2017, 09:18:26 am
content: First post, so helloI've been using the 2N5485 from Tayda as a lazy substitute for the MPF102, J310 etc in projects. Seem to be well-labelled genuine Fairchild devices. They apparently work well into the UHF region although I haven't pushed them past 144MHz-ish (2m band). I bought 20 of them and haven't got through half yet.http://www.taydaelectronics.com/t-transistors/2n-series/2n5485-jfet-n-channel-transistor.htmlYou can get them here quicker in the UK for a higher price:https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=140_151_154&products_id=1076

author: CJay
author_rank: Super Contributor
timestamp: July 28, 2017, 03:29:52 pm
content: Quote from: Alex Nikitin on July 28, 2017, 08:59:30 amFair play, yes it is but ouch, that's a horrendous price. I got the SOT23 versions for ~18p (arrived today)

author: Wolfgang
author_rank: Super Contributor
timestamp: August 08, 2018, 12:37:44 am
content: Hi,the TO-92 versions are still available, and if you want the with high drain currents, this case is a lot better than SMD.Some broadband, low noise HF amps use 4 x J310 in parallel, with good results and low noisehttps://electronicprojectsforfun.wordpress.com/rf-module-gallery/the-amplifier-module-gallery/a-quad-jfet-hf-amplifier/

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 08, 2018, 01:23:39 am
content: I know it does not help you, but i bought a hundred of them a couple years back, I have a life times supply. Its probably time to pick a few essential through hole devices you like to use often in your homebrew and stockpile them, the same goes for the larger size SMD packages, they to are getting harder to get.

author: CJay
author_rank: Super Contributor
timestamp: August 08, 2018, 06:17:13 am
content: I've stocked up on SMD versions so I'm good for a few years but I've also found through hole alternatives which seem to work quite nicely (can't remeber the part number right now but I'll post it later when I get home)

author: VSV_electron
author_rank: Regular Contributor
timestamp: May 16, 2024, 01:34:27 pm
content: Quote from: CJay on August 08, 2018, 06:17:13 amHave you got home by now?

author: Wolfgang
author_rank: Super Contributor
timestamp: May 16, 2024, 01:46:25 pm
content: BF245?

author: profdc9
author_rank: Frequent Contributor
timestamp: May 20, 2024, 01:06:40 am
content: [For some of my projects, I will create "dual" footprints that take both the surface mount (SOT-23 for example) and through-hole (TO-92 wide) so thatThe kicad footprint is attached

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2024, 04:47:17 am
content: I am thinking they need to make a SMT to through hole adapter.I think if you use solder terminals, braze on the wire, then stake into place on the PCB, it will be good. The main problem is it coming apart when you solder it since it would need to be as small as possible.The smallest size keystone solder post that has wire brazed on with low temp silver braze should make for a very small package with the same characteristics as a TH transistor, at a price. Then it needs not be planar. the board would sit upright. It should be very strong if made with staking and braze. Ordinarily the problem would be that the wires come off when you solder on the part, etc. It would look a tiny bit goofy. But I don't see any good way to get wire to attach to a PCB with the similar reliability levels to a TH part. Then you could even use heavy PCB, or flashlight PCB (alumium) and put a heat sink on the backWhen its staked, put 2 in front of PCB and middle one in back, so the wiring natually comes out like a triangle. You could also use brass wire this way if you don't mind the resistance to make it stronger and stiffer.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 20, 2024, 08:44:26 am
content: It is rare that one really needs THT. Most RF circuits are SMD anyway. It would only be prototypes and even there a common techique is using tiny PCBs for circuit elements (e.g. 1 mixer, 1 amplifier stage,...) mounted on the ground plane PCB for the rest.The adaters would be more a thing for a bread board and more LF use. The J310 is also not that bad at lower frequencies, just inconvenient that it may oscillate at rather high frequencies.

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2024, 08:46:39 am
content: doing that upside down soldering shit on a regular basis is a good way to get into bellevue. if you don't need the frequency then use a adapter for gods sake. I got adapters for all the common stuff but not 3 leg components yetI totally do not blame anyone for not wanting to upside down solder tiny parts, its border line insane to do so and align tiny wires etc, and its fragile as hell, and gluing down tiny pads is also loony tunes. You are supposed to be able to kick a leg out, bend it, and twist a component on it. its fast its like tying knots, you can do it almost blind and you won't get eye fatigue unless your being cray with the lead lengths. its not remotely as fun, convenient or low effort as TH type parts.

author: tggzzz
author_rank: Super Contributor
timestamp: May 20, 2024, 08:58:25 am
content: Quote from: Kleinstein on May 20, 2024, 08:44:26 amSimilar example with a 2N3904 BJT andsolderlessbreadboard:https://entertaininghacks.wordpress.com/2024/03/16/practical-traps-with-a-one-transistor-audio-amplifier-solderless-breadboards-and-oscilloscopes/Other types of breadboard are less likely to exhibit such problems