Fake CD4011BE ??? - Page 1
Forum section: electronics / projects

author: mij59
author_rank: Frequent Contributor
timestamp: June 21, 2014, 04:45:47 pm
content: Hi, yes i know i shouldn't but i did buy some cmos ic's CD4011BE on Ebay in China.I tested 10 items and measured a quiescent current of 50 to 66 uA with all inputs low and 0,0 uA with all inputs high at VDD =12V.No loads are connected to the outputs.The quiescent current of 50 to 66 uA is way too high.Any ideas on what is going on here?Thanks.

author: Jon86
author_rank: Frequent Contributor
timestamp: June 21, 2014, 04:48:44 pm
content: Well you answered your own question didn't you.

author: edavid
author_rank: Super Contributor
timestamp: June 21, 2014, 04:58:31 pm
content: How low is low? Are the inputs just wired to ground?

author: SeanB
author_rank: Super Contributor
timestamp: June 21, 2014, 05:11:15 pm
content: Probably a bad batch with high leakage through the internal diodes. Still likely to be working, but they might be either production test rejects or recycled devices. Photos will show that.That leakage is high, but might still be usable in straight logic. Try pulling each input low at a time till you find the leaky one, it might be an internal transistor that is leaking.

author: mij59
author_rank: Frequent Contributor
timestamp: June 22, 2014, 08:58:44 am
content: Quote from: SeanB on June 21, 2014, 05:11:15 pmThank you.Tested an other ic, the quiescence current per gate is about 20 uA, no current is flowing in the input pin , so its must be an internal leak.Apart from the leaking problem the gates are fully functional, e.g. a rise and fall time of 15 nsec.I have attached a photo of dip package .

author: amyk
author_rank: Super Contributor
timestamp: June 22, 2014, 12:07:33 pm
content: Probably not fake, but the higher leakage could be from some minor ESD damage.I wouldn't worry about it unless the extra few dozen uA are critical to your application. (TTL draws about 100x more current...)

author: dannyf
author_rank: Super Contributor
timestamp: June 22, 2014, 12:14:30 pm
content: Unless 50ua idle current matters, this fake sounds everybit as good as the real deal.

author: Paul Price
author_rank: Super Contributor
timestamp: June 22, 2014, 01:13:58 pm
content: Way out of spec!

author: mij59
author_rank: Frequent Contributor
timestamp: June 22, 2014, 01:15:41 pm
content: Quote from: amyk on June 22, 2014, 12:07:33 pmThank you.I hope it is not an ESD problem, could result in reliability issues.My master/slave circuit did not power up, the "power supply" can only deliver 10 uA.

author: SeanB
author_rank: Super Contributor
timestamp: June 22, 2014, 01:27:28 pm
content: With high leakage failure down the line is likely sooner or later. Use a socket if you want to use them so replacing is easy.

author: Paul Price
author_rank: Super Contributor
timestamp: June 22, 2014, 01:58:13 pm
content: Might be you have bought some radiation-hardened 4011 chips left over from a Chinese nuclear power plant or atomic bomb development program.The effect of high radiation exposure would explain the excessive quiescent current.

author: edavid
author_rank: Super Contributor
timestamp: June 22, 2014, 02:18:51 pm
content: Quote from: Paul Price on June 22, 2014, 01:13:58 pmThe spec is at Vin = 0. OP didn't answer the question of what his input voltage was when he measured the 66uA.

author: mij59
author_rank: Frequent Contributor
timestamp: June 22, 2014, 02:29:37 pm
content: Quote from: edavid on June 22, 2014, 02:18:51 pmThank you.Low = VSS = 0VHigh = VDD = 12V