IRLZ44N "Logic-Level" FET from eBay: fake, broken or misunderstood? - Page 1
Forum section: electronics / beginners

author: jypma
author_rank: Contributor
timestamp: April 30, 2013, 05:50:40 am
content: In an attempt to switch some 12V LED strips from my 3.3V microcontroller, I bought some IRLZ44N FETs off eBay, hoping to directly switch them on 3.3V. Maybe eBay was a bad callDatasheet:http://www.irf.com/product-info/datasheets/data/irlz44n.pdfIt seems to claim that 3.3V is enough to saturate the FET in order to deliver the 1A required for the LED strip.In my original test circuit, I connected the micro's 3.3V port output through 100Ohm onto the gate, a 100k pulldown on the gate, source directly onto ground, and drain directly onto "-" of the LED strip. "+" of the LED strip goes to +12V.In 7 out of 10 FETs, only very little current flows (about 1 mA). In the 3 others, I get 0.7A, close enough to light up the strip fully.If I increase the gate voltage to 6V, all FETs switch on fully.Removing the pulldown and gate resistors has no effect.What could be going on here? Are the FETs damaged, mislabeled, or am I misunderstanding the datasheet completely?Any help will be greatly appreciated.

author: ejeffrey
author_rank: Super Contributor
timestamp: April 30, 2013, 06:12:17 am
content: Probably fakes. I've never bought semiconductors off of ebay, but apparently fakes are quite common. You are lucky you got what appears to be a FET at allThere are other possibilities, like ESD damage, too little voltage for the LED strip, or circuit oscillations, but turning on OK at 6 V strongly suggests they are just lesser devices remarked.

author: amyk
author_rank: Super Contributor
timestamp: April 30, 2013, 10:16:51 am
content: What do they look like? Post some pictures.

author: sorin
author_rank: Frequent Contributor
timestamp: April 30, 2013, 03:47:53 pm
content: Quote from: AcHmed99 on April 30, 2013, 11:15:42 amAre you kidding, the shipping cost for example in my country is over $50

author: sleemanj
author_rank: Super Contributor
timestamp: April 30, 2013, 04:07:29 pm
content: Quote from: jypma on April 30, 2013, 05:50:40 amGiven that some do work close to what you expect, and some don't work anything remotely like it, and pushing the gate to 6v makes all of them work, I would hazard a guess that you've probably been sold ones from the reject bin at the factory.I have to say, AcHmed99's suggested NXP FET looks to be a really nice little unit. RS sells it in packs of 10, and they do free shipping here in NZ - don't know about in their other territories.

author: G7PSK
author_rank: Super Contributor
timestamp: April 30, 2013, 08:24:03 pm
content: Last time I ordered from Farnell in the UK I had to have an order of £58-00 or above for free shipping, that rules them out for just a few transistors or what have you postage is £8-00.

author: codeboy2k
author_rank: Super Contributor
timestamp: May 01, 2013, 12:48:06 am
content: and those NXPs AcHmed99 pointed out are even on sale now at just over 0.19 each...can get 100 for $19, almost tempted to buy 100 to make these my new jelly beans for a whileCheaper than the SN7002, super low Vth, fully enhanced at Vgs=4.5V, decent Rds(on) at Vgs=1.8V and Id<500ma,and more area under the SOA DC line than the 7002 = wider operating range =

author: mariush
author_rank: Super Contributor
timestamp: May 01, 2013, 01:22:15 am
content: sorin, newark.com is the US site of FarnellIn Europe you can use farnell.com , same company. Also tryhttp://export.farnell.comand if that fails, see element14.com , same company Farnell but I think mostly used only in Asia.There's also rs-online.com :http://www.rs-online.com/index.htmlClick on Other Countries and see what they charge for parts. For me in Romania, they charge 5 euro shipping, but I prefer Farnell because they ship directly to me - rs-online ship to a local distributor, which then couriers me the parts (all included in the 5 euro shipping fee) so it takes more time.Farnell doesn't do free shipping for Romania but it's not expensive at 20 RON (about 4.5 euro) per package.

author: David_AVD
author_rank: Super Contributor
timestamp: May 01, 2013, 02:19:47 am
content: Yeah, I've never been keen on buying components off eBay. I wonder how many people get frustrated with their circuit when it's really (unknown to them) a case of dodgy parts?

author: jypma
author_rank: Contributor
timestamp: May 02, 2013, 05:53:09 am
content: Thanks for all the help! Here's a pictureI live in Denmark, which has a pretty high VAT tax (25%) on all imported goods, _if_ they are over about $10 in value. But, regardless of value, you _always_ pay about $25 in "import handling fees" just to get your package evaluated.Amongst digikey, mouser, etc. I have yet to find a supplier where there isn't effectively a very high post-delivery price to pay, since they all use "big shiny" shipping agencies. Plus, from what I've heared, with them you end up paying the 25%+fees even if the value is below $10.At least most ebay packages seem to be able to slip under the radar...I have learned my lesson regardless, think I will use Conrad for the next order, they have to-consumer shipping, and are within the EU, so no hidden costs.

author: Ghydda
author_rank: Regular Contributor
timestamp: May 02, 2013, 07:45:40 am
content: It's true about the awful component situation i DenmarkThat is why I use eBay extensively for acquiring components. I am however always careful when picking the seller to buy from. I generally avoid any seller which does not have like +25k deals on the odometer and an above 99.5 rating.Once in a while some stuff is difficult to come by at a reasonable price among the reputable eBay sellers - then I go look for those less reputable sellers, always keeping in mind I may receive a duff.Another tip useful for local folks in Denmark isthis site. I've used this seller a lot and although he is expensive (compared to eBay) many items drop significantly in price once you order like 10 or 100 of each itemVery useful when building up a basic stock of often used generic parts.

author: amyk
author_rank: Super Contributor
timestamp: May 02, 2013, 09:57:45 am
content: According to IR's part marking info, those have a datecode of week 18, 2002 and are lead-free?

author: ptricks
author_rank: Frequent Contributor
timestamp: May 02, 2013, 11:55:09 am
content: It is okay to buy parts off ebay , just use sellers that you trust. Here are a few that I regularly order from :abcfab, remote*control, nooelec,memotronics_llc,chrisgrxThe last seller I listed has good prices on hook up wire and fair prices on other stuff.Really easy way to tell the quality of the parts being sold, if the seller is also selling clothing and jewelry or items not related to electronics, you might want to think twice.

author: FoXX
author_rank: Contributor
timestamp: May 02, 2013, 12:03:00 pm
content: If in Denmark then why not use Elextra?Elextra.dk

author: Ghydda
author_rank: Regular Contributor
timestamp: May 02, 2013, 01:19:15 pm
content: Quote from: AcHmed99 on May 02, 2013, 10:05:04 amThere is more to it. Farnell is represented in Denmark with their own local branch so obv. VAT appliesNow Amazon for instance has no presence in Denmark - then one would assume the VAT burden is lifted. But noooooo...Any foreign company (regardless of having a presence within the EU or not AFIAK) which export goods to Denmark for a certain amount annually (which from what I understand is way less than a 100.000 us$) is required to register with the Danish tax authorities and comply with our tax laws - and thus Amazon are sticking to the rules of engagement and charges Danish sales tax on any item they sell and ship into Denmark and in the process hands over the VAT-amount to the Danish tax authoritiesAnd here is the real stickler, the shipping and handling is also VAT'ed as this is a service that was purchased along with the physical goodsThis might also apply elsewhere in the world but considering our VAT is 25% that can significantly increase the total cost of getting stuff from the other side of the pond. Oh well...