
Fake audiophile opamps: OPA627 (AD744?) - atomlib
http://zeptobars.ru/en/read/OPA627-AD744-real-vs-fake-china-ebay
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leephillips
Counterfeiting of chips is such a big problem that the US DARPA has a major
program to develop tiny cryptographic chips that can be embedded inside chip
packages to prove their authenticity. It's called the SHIELD program
(solicitation number DARPA-BAA-14-16 if you want to ask for money).

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malandrew
I'm not an EE, but I imagine that a much better solution would be a universal
device where you can connect a chip and run a publicly available test suite
against the chip to confirm that is performs as expected.

Like @wyager, I'm extremely skeptical of a program like SHIELD.

~~~
leephillips
They think that the embedded chip (which they call a dielet), which responds
to a crytographic challenge from a handheld device on an assembly line, can
avoid testing, which is much more time consuming and complicated. To test, you
need to connect the device's pins to something and power it on. These devices
are for military systems: you'll need to test lifespan and performance under a
variety of environmental conditions. I don't know if the dielet idea will work
out, but it's specifically to verify authenticity without having to test.

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natejenkins
Can someone point out where are the laser trimmed resistors in the photos, and
maybe explain some more of the components?

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cc_
If you're interested in this sort of thing, there is a great class at RPI
which has its lecture slides available:

[http://security.cs.rpi.edu/courses/hwre-
spring2014/](http://security.cs.rpi.edu/courses/hwre-spring2014/)

The slides for lecture 4 ([http://security.cs.rpi.edu/courses/hwre-
spring2014/Lecture4_...](http://security.cs.rpi.edu/courses/hwre-
spring2014/Lecture4_Layout.pdf)) shows what various types of components (such
as laser-trimmed resistors) look like on a die.

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natejenkins
I am and this looks awesome. Thank you!

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joosters
If you can't tell the difference without dissolving the chip in acid...
perhaps then there is no difference?

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thrownaway2424
The interesting thing here is that the part has been substituted with another
part that's comparable in quality and only slightly less expensive. The
margins for counterfeiting this part can't have been very good.

It's pretty common to counterfeit electronic parts. I've come across
counterfeit op-amps, exotic transistors, power transistors, ordinary
transistors, capacitors, and even fake resistors which is amazing. It always
just makes me wonder what is wrong, collectively and institutionally, with
China? Making counterfeit goods of all kinds is apparently a common line of
business in China. Is it just because _everything_ is made there so
counterfeiting has proportionately shifted there as well?

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mschuster91
Fake resistors? How is one supposed to fake a resistor? There are no
manufacturer markings on them, just (easily testable) resistance/precision
indicators...

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yitchelle
Resistor is more than resistance. There is also other characteristics like
power capacity, accuracy, tolerance, frequency responses, temperature
coefficient etc.

The cheaper resistors are typically very loose for most of these
characteristics. A tight characteristics means a high level of quality control
at manufacturing, and this is usually lacking for the fakes.

For Op-Amps, the interesting spec is their frequency response as the op amps
are not typically used in DC situations.

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cnvogel
Especially if you get a batch that was manufactured in the original factory,
and the faulty one put on the grey market. Indistinguishable product, but
guaranteed and tested to be out of spec (might be a important parameter, or
not).

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boise
Best to only buy from TI franchised suppliers. Can't find any that go down to
$16 though

[http://octopart.com/opa627au-
texas+instruments-420817](http://octopart.com/opa627au-
texas+instruments-420817)

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GFK_of_xmaspast
"Hey! This is lizard oil, not snake oil!"

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njharman
til; that resistors are trimmed with lasers
[http://en.wikipedia.org/wiki/Laser_trimming](http://en.wikipedia.org/wiki/Laser_trimming)

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Terr_
They also may use lasers to trim and tune the mostly-crystal oscillators used
in timing circuits, such as the small quartz "tuning fork" found in many
digital watches.

[http://en.wikipedia.org/wiki/File:Inside_QuartzCrystal-
Tunin...](http://en.wikipedia.org/wiki/File:Inside_QuartzCrystal-
Tuningfork.jpg)

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Johan-bjareholt
I have previously bought two of these chips and they sound pretty good, sad
that they are fake though.

Will buy the genuine one for comparison, will see if I can hear any sound
quality difference

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darksim905
How do they get such high resolution? An electron microscope or something?
Such a cool blog, I've seen it featured on HaD a few times.

~~~
ableal
Analog circuits are fairly big, this is taken with a regular microscope. You
can see that the chip is a few millimeters square.

Besides, electron microscope pictures are monochromatic.

