Best NPN fet? Cheapest? What do you use? - Page 1
Forum section: electronics / beginners

author: EEVPiobee
author_rank: Contributor
timestamp: February 12, 2014, 01:21:28 pm
content: Quick survey, (Translate: I need suggestions)What is the best and absolutely cheapest NPN Fet you know ?(TO-92 package, Source-Drain 12vDC, really doesn't draw lots of amps ugh... miliamps, Gate is Fed with 3.3 to 5.5 volts PWM)Thank you in advance for your suggestions!

author: c4757p
author_rank: Super Contributor
timestamp: February 12, 2014, 01:27:35 pm
content: For that purpose, try 2N7000.And it's "N-channel", not "NPN":

author: sleemanj
author_rank: Super Contributor
timestamp: February 12, 2014, 01:39:37 pm
content: Quote from: EEVPiobee on February 12, 2014, 01:21:28 pmBah, if you don't need high current or high power, why on earth use through hole!This is 2014 not 1980's :-)SMD mosfets are far cheaper than through hole ones and logic level mosfets are easier to find in SMD forms.The SOT-23 form Si2302DS is ridiculously cheap, and only 115 milliohm RDSon at 2.5v Vgs, down to 85 milliohm at 4.5 Vgs.

author: EEVPiobee
author_rank: Contributor
timestamp: February 12, 2014, 01:59:41 pm
content: Quote from: sleemanj on February 12, 2014, 01:39:37 pmSleemanj:Because I'll be using a lot of those in myhand soldered(first versions) prototypes..(To be clear: I don't plan to run mass production at first on anything right now, If I ever do so, I'll check up on switching my parts to surface mount)But thank you for your part suggestion, I'll keep that in mind

author: sleemanj
author_rank: Super Contributor
timestamp: February 12, 2014, 02:06:52 pm
content: Quote from: EEVPiobee on February 12, 2014, 01:59:41 pmOnce you've done one or two you can hand solder SOT-23 faster than you can hand solder a through hole device.Don't be scared of surface mount, it's a lot easier than you think, with any crusty old soldering iron.And if you are etching your own prototypes, WAAAAAY easier to use surface mount when ever you can, drilling holes sucks.

author: ConKbot
author_rank: Super Contributor
timestamp: February 12, 2014, 05:40:14 pm
content: SOT-23-3 fits on 0.1" pad per hole board/veroboard/prototypingboard/whatever you call it/just fine. So if you find one that fits your specs, have at it

author: Monkeh
author_rank: Super Contributor
timestamp: February 13, 2014, 02:36:54 am
content: Quote from: sleemanj on February 12, 2014, 01:39:37 pmBah, terrible performance.Try these:http://www.fairchildsemi.com/ds/FD/FDC637BNZ.pdfOkay, so it's not quite as nice a package.

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 06:16:20 am
content: Quote from: c4757p on February 12, 2014, 01:27:35 pm2N7000 isn't spec-ed as a logic level part.I think VN2222LL is the most common logic level, through hole part. It costs about $0.07.

author: Monkeh
author_rank: Super Contributor
timestamp: February 13, 2014, 06:18:17 am
content: Quote from: edavid on February 13, 2014, 06:16:20 am... from where?

author: mariush
author_rank: Super Contributor
timestamp: February 13, 2014, 07:08:44 am
content: I don't understand what's wrong with 2n7000. Maybe you can explain.There's alsobs270that costs about 8 cents each if you get 1000 (under 13 us cents if buying 100 or more)

author: sleemanj
author_rank: Super Contributor
timestamp: February 13, 2014, 07:23:34 am
content: Quote from: mariush on February 13, 2014, 07:08:44 amHigh drain source resistance at logic levels gate to source, 2R or more easily. And of course that drastically limits the current capability at those levels - 500mA through a 2R Rds is half a watt, which is exceeding the maximums.Edit to add: but it's still seems better than the VN2222 suggested above... 7R+ RdsOn

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 04:27:14 pm
content: Quote from: Monkeh on February 13, 2014, 06:18:17 amArrow, Future, etc.http://www.findchips.com/search/vn2222llhttp://components.arrow.com/part/detail/40924479S7076271N5236

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 04:33:01 pm
content: Quote from: mariush on February 13, 2014, 07:08:44 amThe OP said he wants a part for logic level use. On the 2N7000 datasheets I checked, there's no spec for RDSat logic level VGS.QuoteNice, it's $0.04 from Arrow etc. and it has a spec for VGS= 4.5V.

author: Monkeh
author_rank: Super Contributor
timestamp: February 13, 2014, 06:21:11 pm
content: Quote from: edavid on February 13, 2014, 04:27:14 pmAh. I tend to forget about companies who are unfeasibly expensive to place orders <$200 with.

author: c4757p
author_rank: Super Contributor
timestamp: February 13, 2014, 06:42:26 pm
content: Quote from: edavid on February 13, 2014, 06:16:20 amFor "milliamps" it is. At 1mA the Fairchild datasheet lists the threshold as 2.1V typ, 3V max.

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 07:17:38 pm
content: Quote from: Monkeh on February 13, 2014, 06:21:11 pmIn the US, Arrow charges $8 flat rate shipping (and sometimes they have free shipping promotions). What do they charge in the UK?

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 07:18:40 pm
content: Quote from: c4757p on February 13, 2014, 06:42:26 pmBut there's no logic level RDSspecWhy not use a part that's specified for what you want to do?

author: Monkeh
author_rank: Super Contributor
timestamp: February 13, 2014, 07:23:34 pm
content: Quote from: edavid on February 13, 2014, 07:17:38 pmTo get the prices you're finding? $28 minimum, 20% VAT on top of that. European branch is more expensive and doesn't hold the same components in stock, and so far I can't even find their shipping charges. Arrow, Future, Digikey, Mouser, all pretty much pointless unless you spend fairly significant sums (Digikey and Mouser will do free delivery if you spend enough, iirc), Arrow and Future you need to spend hundreds at before it's worthwhile because of shipping costs. Not good for hobbyists.I still stand by my insanely cheap FDC637BNZs (no idea why they're so cheap at Farnell.. no idea why VN2222LLs are so cheap at Arrow.).

author: edavid
author_rank: Super Contributor
timestamp: February 13, 2014, 08:22:42 pm
content: Quote from: Monkeh on February 13, 2014, 07:23:34 pmI guess this just shows why the OP should set the country in his profile!

author: EEVPiobee
author_rank: Contributor
timestamp: February 15, 2014, 06:53:06 am
content: Quote from: edavid on February 13, 2014, 08:22:42 pmThanks for noticing, I just didQuote from: edavid on February 13, 2014, 04:33:01 pmWell actually, I'm using PWM just to dim a led (for this application...) the absolute cheapest is fine to me!! (Althoung I didn't try anything yet...)

author: Zero999
author_rank: Super Contributor
timestamp: February 16, 2014, 04:49:44 pm
content: The 2N7000 has one main advantage over many of the other parts mentioned: low gate capacitance: typically only 20pF. So far the only part mentioned which beats this is the 2SK3541.

author: mariush
author_rank: Super Contributor
timestamp: February 16, 2014, 06:11:59 pm
content: Same for the BAS270 i mentioned:http://www.farnell.com/datasheets/104927.pdf20pF typically, 50pF maximum

author: edavid
author_rank: Super Contributor
timestamp: February 16, 2014, 08:44:41 pm
content: Quote from: Hero999 on February 16, 2014, 04:49:44 pm2N7000 = 20pF typ/50pF max, BS270 = 20pF typ/50pF max, VN2222LL = 60pF max. No real difference.

author: mrflibble
author_rank: Super Contributor
timestamp: March 22, 2015, 03:42:51 pm
content: Quote from: AcHmed99 on February 16, 2014, 06:45:11 pmJust in case you or anyone else is looking to buy, Mouser currently stocks the NTS4001 for about that nickel or so a pop, at 100 quantity. Digikey also has them, but at roughly double the cost.

author: dannyf
author_rank: Super Contributor
timestamp: March 22, 2015, 04:32:27 pm
content: QuoteFor npns, 2n2222 and 3904 are dime a dozen.For fets, 2n7002.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 22, 2015, 09:30:38 pm
content: AO3400 33mOhm @ 4.5Vgs, 1nF max Cgs though, few KHz PWM should be fine... the fun part is... that sot23 tiny little bastard can pass 5A like nothing so the DS said. 8 US cents in 100qty...http://www.ebay.com.my/itm/171177440326?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

author: Christopher
author_rank: Frequent Contributor
timestamp: March 22, 2015, 09:41:08 pm
content: I remember using a 2n7002 (which is apparantly now obsolete) to switch a relay which drew 400ma... magic smoke time!2n7000 will be fine, if you can handle the rds on (if your leds are low current it'll be fine)

author: Cliff Matthews
author_rank: Unknown
timestamp: March 22, 2015, 09:50:35 pm
content: Quote from: Mechatrommer on March 22, 2015, 09:30:38 pmWow! When I finally make my trip into SMD, a strip of those will be my first victims

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 28, 2015, 06:37:30 am
content: i just figured out from a circuit... TPCA8028 in somekind of mini soic?... darn 2mOhm Rdson, darn 50Abut the datasheet i just downloaded say "not suitable for new design" must be obsoleted, must gotta have new chip with that kinda performance, gotta look for it sometime... so thats how they did it in 60A ESC...