fake and/or mislabelled lm311 :) - Page 1
Forum section: electronics / general

author: Redeeman
author_rank: Contributor
timestamp: September 19, 2015, 09:32:56 pm
content: Hellobought some lm311 comparators off ebay, and wellthey didnt quite work out as one might have expected(well depending on ones opinion of chinabay).in any case, they are not lm311, they are in fact dual opamps, and their response are exactly similar to some lm358's i have lying around.the print says lm311 though

author: Psi
author_rank: Super Contributor
timestamp: September 20, 2015, 04:44:50 am
content: And what this the ebay sellers feedback and number of sales...Im going to guess low and very few

author: Bud
author_rank: Super Contributor
timestamp: September 20, 2015, 04:48:21 am
content: Quote from: blueskull on September 20, 2015, 04:40:00 amWhere do everyone source parts from in China ?

author: fivefish
author_rank: Frequent Contributor
timestamp: September 20, 2015, 05:26:21 am
content: Thing with Chinese parts is I suspect some of these parts failed QA testing, or didn't meet spec, and then instead of being destroyed, they find it's way to these unauthorized sellers/distributors. They then sell it at a cheap price on eBay, etc.So... if your project is not pushing these parts hard, it may work on your project just fine and you'd think nothing of it.Example: I bought some power transistors on eBay, supposedly rated 12A Collector current, but they fail before 4A is even reached. I know my design works, so got the same transistor part from Mouser, and I was able to reach my goal of 6+Amp without any problem... it runs cooler too vs. the eBay/China part.

author: fivefish
author_rank: Frequent Contributor
timestamp: September 20, 2015, 07:19:11 am
content: Thing with Chinese parts is I suspect some of these parts failed QA testing, or didn't meet specSorry, I wasn't clear enough. I wasn't referring to the LM311 in the OP, but to power transistors in general.

author: wraper
author_rank: Unknown
timestamp: September 20, 2015, 07:58:37 am
content: Quote from: fivefish on September 20, 2015, 07:19:11 amThere are very tiny numbers of rejects if any. Most of out of spec parts are just fakes, and for some parts it is almost impossible to buy genuine from China. For example, try to buy genuine OPA627 from china, good luckAt best, you'd get some rejects if they cannot just sell whatever else on the first look functioning like normal stuff, like ADCs.

author: Redeeman
author_rank: Contributor
timestamp: September 20, 2015, 08:12:27 am
content: this specific ebay dealer had 20k sales and 99.5% positive. i wrote to him explaining it, and he said it didnt happen before, and he will send 20 new

author: Psi
author_rank: Super Contributor
timestamp: September 20, 2015, 08:41:10 am
content: ah, well that's ok then.Im totally ok with ebay sellers making mistakes as long as they fix them.

author: rob77
author_rank: Super Contributor
timestamp: September 20, 2015, 09:32:33 am
content: if you decided to use LM311, then i assume it's because it's speed and low input current of the genuine TI part... so why from e-bay ? the genuine LM311P (115ns version in DIP package) from TI is approx euro 20cents , SMT versions start at 9 cents.for simple designs where speed , input current, offset and power consumption is not critical (e.g. comparator to light up a LED when a threshold is reached) - for those cases the knock-off/fake/rejects from china are OK.edit:i meant 20 euro-cents - or 0.2 Eur

author: wraper
author_rank: Unknown
timestamp: September 20, 2015, 09:37:27 am
content: Quote from: Redeeman on September 20, 2015, 08:12:27 amThey always say that when complaining about counterfeits.

author: wraper
author_rank: Unknown
timestamp: September 20, 2015, 10:09:43 am
content: Quote from: blueskull on September 20, 2015, 09:57:52 amHence the market to sell fake OPA627 for clueless audiofools. Those idiots even claim to be able to distinguish this single opamp in audio path by sound. Like they never mix up sound of one compared to another. I'd like to run blind tests on those people, IMO most of those golden ears wouldn't distinguish OPA627 from LM358.

author: rob77
author_rank: Super Contributor
timestamp: September 20, 2015, 10:15:35 am
content: Quote from: blueskull on September 20, 2015, 09:57:52 amactually the metal can and ceramic are MUCH better than plastic.... the super-zener LTZ1000 is in a CAN for a VERY good reason, same for the ultra-low input current opamps (used e.g. input amp for STM). with cans and ceramic you have much less thermal expansion and much lower leakage currents.

author: SeanB
author_rank: Super Contributor
timestamp: September 20, 2015, 11:04:05 am
content: CERDIP and can has an advantage over moulded only in niche applications, as the die inside has less stress imposed on it from the residual forces in the plastic. Will affect a precision voltage reference ( not a TL431) and possibly a ultra precision opamp or ADC, otherwise the designer should have compensated for this. Only if you really need all resistors on the die to track to within 1 PPM over -55 to +125C and all transistors to do the same will you notice a difference. On most parts drawing 1mA more out of the one output will have a larger effect on performance. Only thing to note is that the smaller packages are worse for being affected by light and humidity being absorbed by the plastic, but even that is an adge case.

author: rob77
author_rank: Super Contributor
timestamp: September 20, 2015, 12:18:12 pm
content: Quote from: blueskull on September 20, 2015, 10:52:11 amthen explain why opamps like OPA111 , OPA128, AD515, AD549 are available ONLY in cans

author: Redeeman
author_rank: Contributor
timestamp: September 20, 2015, 02:27:48 pm
content: wellto be honest my purpose in buying these was just playing aroundso dont really NEED them for their properties, but well

author: Vgkid
author_rank: Super Contributor
timestamp: September 20, 2015, 07:01:34 pm
content: Look at something like the lmp7721, a 3fA opamp, in soic8http://www.ti.com/lit/ds/symlink/lmp7721.pdf

author: Tandy
author_rank: Frequent Contributor
timestamp: September 20, 2015, 07:34:46 pm
content: Trouble is everyone is always after a bargain, as they say if it looks too good to be true it probably is.I know I am always a bit sceptical when manufacturers try and convince you to buy official products for your country but there does seem to be a lot of fraud in the electronic components business. At the end of the day if you try and build an actual product from components that you didn't get from a reputable source, it is not a question of if, but when you will get burnt.

author: Redeeman
author_rank: Contributor
timestamp: October 05, 2015, 08:28:47 pm
content: wellthe replacements came today, only a minor issue, they are every bit as fake as the firstbut this time in significantly worse physical condition

author: kfnight
author_rank: Regular Contributor
timestamp: October 05, 2015, 08:32:38 pm
content: Quote from: Redeeman on October 05, 2015, 08:28:47 pmThey might have well sent you a box of rusty nails.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 05, 2015, 09:20:08 pm
content: The first one seems to have touched-up pins. The second almost looks like it was blacktopped.http://www.asq.org/asd/2009/03/compliance/counterfeit-parts.pdf

author: Delta
author_rank: Super Contributor
timestamp: October 05, 2015, 11:04:51 pm
content: Good on 'em. I'd much rather see parts pulled than entire boards end up in landfill...

author: Redeeman
author_rank: Contributor
timestamp: October 07, 2015, 07:40:35 pm
content: i can confirm that the top of the chips look more black than the bottom, and that i have inspected other TI parts i have which have same color on bottom and top.pretty sure thats whats going onwell... not a huge loss, only ordered them for fun from ebay, its more the idea of it

author: felixna
author_rank: Newbie
timestamp: February 10, 2017, 05:51:36 pm
content: I also got some fake LM311 chips from ebay:The fake LM311 is a dual OpAmp (slope rate 0,5V/usec, Vout between Vcc-1,7V and Vee+1,2V, but not very fast).I can't confirm that the top is darker than the buttom but the TI-Logo looks different than the logo on an original chip I bought:

author: Cubdriver
author_rank: Unknown
timestamp: February 10, 2017, 07:29:02 pm
content: Quote from: Redeeman on October 05, 2015, 08:28:47 pmI hope that you plan to give him appropriate feedback...-Pat