is this a fake ad8032 opamp? - Page 1
Forum section: electronics / projects

author: exe
author_rank: Unknown
timestamp: November 05, 2017, 07:21:31 pm
content: Hello everybody,I wanted to play a bit with ad8032 opamp. But they are quite expensive. So I bought a few ad8032 from aliexpress....The thing is, it doesn't work as expected. I constructed a unity gain amplifier to check the output swing. The first opamp was too close to negative rail (very close), but too far off from the positive rail (~0.6V gap) comparing to what datasheet says. Output not loaded.So I tried another one, and look what I see (attachment). When input signal comes within ~0.5V to positive rail, the output wildly jumps very close to positive rail. It also oscillates a lot if I directly connect Vout to inverting input. Oscillations gone if I use 1.5K resistor instead. All constructed on breadboard, but decoupling cap (100nF) directly connected to power pins. Input bias current ~1uA.My questions are:1) Does it look like a fake?2) Can I assume the second device is defective? (the one I provide the scope picture)3) what opamp this could be?

author: wraper
author_rank: Unknown
timestamp: November 05, 2017, 07:45:58 pm
content: If you buy opamp from China for 2x cheaper than cheapest quantity of 100 at places like mouser or digikey, it's almost guaranteed to be counterfeit. What it is? Hard to say but you first need to show a photo top and bottom. Try to rub top of the IC with some solvent like acetone. I would never buy opamps from China, you can get even counterfeit LM358.

author: exe
author_rank: Unknown
timestamp: November 05, 2017, 08:29:01 pm
content: Quote from: wraper on November 05, 2017, 07:45:58 pmPlease find photos attached. The problem is, I don't know what a genuine part should look like.Opened dispute anyway, I asked the seller before the purchase if it's genuine or not. But the price was too good to be true (~$4 delivered for 5 ICs).

author: danadak
author_rank: Super Contributor
timestamp: November 05, 2017, 09:49:36 pm
content: This is a very fast OpAmp.Driving capacitive loads, see the analog devices datasheet andgraph discussing low amounts of C, like you scope probe andits affects on stability. Page 15.http://www.analog.com/media/en/technical-documentation/data-sheets/AD8031_8032.pdfRegards, Dana.

author: wraper
author_rank: Unknown
timestamp: November 05, 2017, 09:58:20 pm
content: Photos are not very good. However even from this I see that top look to be sanded and bottom is nothing like Analog Devices ICs I've seen.

author: MasterT
author_rank: Frequent Contributor
timestamp: November 05, 2017, 10:43:03 pm
content: Quote from: exe on November 05, 2017, 07:21:31 pm1. Seems fake to me, different package compare to one shown in AD data sheet.2. Not necessarily, I 've seen such abnormal behavior with TI genuine OPA, that is not rail-to-rail on inputs, outputs or both.3. You never know. I bought myself a pack of 10 same ad8032 from ali about a year ago, they were very slow, something <1 MHz GBW, but what impressed me is their outstanding performance in audio path, THD was well below 0.001%

author: amyk
author_rank: Super Contributor
timestamp: November 06, 2017, 12:33:15 am
content: It looks like the fake label they applied is already starting to come off in the lower right corner of your first photo...

author: exe
author_rank: Unknown
timestamp: November 06, 2017, 06:26:30 pm
content: Quote from: amyk on November 06, 2017, 12:33:15 amSorry, that's flux... Unfortunately, this is the best photo I was able to make. I lost my macro lens...

author: bson
author_rank: Unknown
timestamp: November 06, 2017, 08:31:11 pm
content: Price says fake; even recycled parts would cost more. Reel price (2500pc) is slightly under $3, so there is no way these could be sourced low enough that a seller has any margin at $1.25 qty 4! They'd have to find them under $1. Not gonna happen.But I'd still never buy these from a random seller on one of the market sites - because the next one will be smart enough to look up the reel prices and sell their fakes at that plus a 35% markup. They'll possibly also buy a reel (then return it) of the genuine article, so they have a nice invoice to show you on request.

author: wraper
author_rank: Unknown
timestamp: November 06, 2017, 09:05:17 pm
content: Quote from: bson on November 06, 2017, 08:31:11 pmActually you can get genuine at quantity of 100 for slightly above $2.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: November 06, 2017, 09:15:00 pm
content: Quote from: exe on November 05, 2017, 08:29:01 pmPM me your postal address.Leo

author: chris_leyson
author_rank: Super Contributor
timestamp: November 06, 2017, 10:06:03 pm
content: They look very much like fakes, never seen the real thing do that on the output. Haven't used one as a unity gain buffer but they should be unity gain stable with a bit of care. I'm sure I've got a few dual PDIP ones somewhere so will try out a unity gain buffer just for the hell of it. BTW I used a few AD8032s in a prototype single rail 5V galvo controller just to see how well they worked at or near the supply rails as some parts of the control loop would saturate with a step input. They were all fine and performed as expected, eventually replaced them with Microchip MCP6292 as I didn't need the bandwidth.