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How do I tell a fake OPA627 637 from real


sbelyo

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I have several OPA627 and OPA637 in 8 pin dip.  Some I ordered from digikey, some from ebay that could've been digikey samples and some from ebay that aren't.

 

The problem is I acquired some when there were some fakes going around.  I didn't separate one order from another and put them all together.  I'm sure some are real and some are fake but is there a definitive way to tell?

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Measure the resistance between the V+ pin (7) and each of the "trim" pins (5 and 1).

The real ones should all be pretty close, the fakes will not be.  

I'll try that tonight.  I'm sure one or two are fake because the logos aren't straight.  I'll see what happens

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I'll try that tonight.  I'm sure one or two are fake because the logos aren't straight.  I'll see what happens

 

I've had samples from Ti and Analog Devices where the logo weren't straight. As mentioned resistance measurement and possibly even listening can point out the fake from the real pack. 

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I have batch 1

           1 637BP that's 220 Ohms off

           1 637AP that's 400 Ohms off

           1 627AP that's 170 Ohms off

 

I have batch 2

           1 637BP that's 0 Ohms off (dead even)

           1 627BP that's 80 Ohms off

           1 637BP that's 10 Ohms off

 

What do you think?

Edited by sbelyo
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Did you try a similar test (measure with red and black probes one way, then switch them) for the 5&1:7 test?

 

Meters sometimes switch diodes/transistors on and mess everything up.

 

Looking at the datasheet for the 627 I have no idea how this would happen in real life, but it is easier to check both ways than think about :)

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Did you try a similar test (measure with red and black probes one way, then switch them) for the 5&1:7 test?

 

Meters sometimes switch diodes/transistors on and mess everything up.

 

Looking at the datasheet for the 627 I have no idea how this would happen in real life, but it is easier to check both ways than think about :)

I did not keep track of red or black on the 5&1:7 test.  I will retest when I get home as well as test between 5 and 1

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 batch 1 difference between 5&1:7 both ways

           1 637BP that's 220 Ohms off

           1 637AP that's 400 Ohms off

           1 627AP that's 170 Ohms off

Measurement of resistance between 5&1 all fall between 45 - 58K both ways

 

 

batch 2 difference between 5&1:7 both ways

           1 637BP that's 0 Ohms off (dead even)

           1 627BP that's 80 Ohms off

           1 637BP that's 10 Ohms off

Measurement of resistance between 5&1 all fall between 45 - 58K both ways

 

I'm ready to call them all real.  I have no other means to test other than to listen to them in a circuit.  What do you think?

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