checking for fake OPA2134?
- Thread starter lcipher3
- Start date
Cybercow
Well-known member
Testing for current draw merely determines the current draw of the device. Using a DC input in the manner demonstrated in the schematic will not tell anyone if it is a genuine OPA2134 - only that it's an opamp if the Vref measures exactly 1/2 Vcc. And the Texas Instruments OPA2134 has a quiescent current draw of 4 to 5 mA - according to the datasheet.
The OPA2134 is a very clean opamp and I would test the AC signal output instead of just the DC aspect. Connect the power per the spec sheet and connect the output to the negative input terminal, then put an AC signal on the plus input terminal. You should see an exact copy of the input on the output terminal. Some cheap opamps will have a DC offset, so the resultant AC output will not precisely match the input.
The OPA2134 is a very clean opamp and I would test the AC signal output instead of just the DC aspect. Connect the power per the spec sheet and connect the output to the negative input terminal, then put an AC signal on the plus input terminal. You should see an exact copy of the input on the output terminal. Some cheap opamps will have a DC offset, so the resultant AC output will not precisely match the input.
Chuck D. Bones
Circuit Wizard
Measuring current draw is a quick & dirty way to tell if someone has relabeled a TL072.
I also posted pix of a real and a fake. I suppose that the counterfeiters could do a better job with the labeling, but the guys who made that particular fake did a pretty sloppy job of it.
DC offset voltage won't tell you if an opamp is OPA2134 or not because lot of opamps have tight offset voltage specs.
One of the things that distinguishes the OPA2134 is the very low crossover distortion. Not easy to measure and you won't see it looking at a scope trace. You need a distortion analyzer or a spectrum analyzer.
The easiest way to know you have the real deal is to buy it from an authorized distributor.
I also posted pix of a real and a fake. I suppose that the counterfeiters could do a better job with the labeling, but the guys who made that particular fake did a pretty sloppy job of it.
DC offset voltage won't tell you if an opamp is OPA2134 or not because lot of opamps have tight offset voltage specs.
One of the things that distinguishes the OPA2134 is the very low crossover distortion. Not easy to measure and you won't see it looking at a scope trace. You need a distortion analyzer or a spectrum analyzer.
The easiest way to know you have the real deal is to buy it from an authorized distributor.
That was my thoughts - TL072 would be the most likely one to use as a "fake" and the ~ 8 mA (2x4mA in a dip8) would be a "rough" check.
I actually remembered I had a stash I bought 10 years ago from Digikey so I'm pretty sure they're good ones.
Chuck D. Bones
Circuit Wizard
DigiKey doesn't sell fakes. If you got them from DigiKey, they're good. eBay sellers... ya never know. Some eBay sellers have no idea what they're selling, others deliberately sell counterfeit parts. It's possible to buy good electronic components on eBay, I've done it, but it's a gamble. Like the saying goes: "If the price is too good to be true..."
This thread was helpful to me. I just finished my General Tso build and have some strange behavior/noise that I was debugging. This lead me down to considering the OPA2134 I got from Tayda as a culprit.
The photo shows a pretty poor looking BB logo (regular font?) and a missing pin 1 indent?
So I setup the quiescent current sanity check test with the OPA2134 and some TL072 I have on hand (also from Tayda)
The results weren't promising:
TL072 checked out pretty normal/to spec ~ 4.5ma, so ~2.25 per amplifier, datasheet says 1.4-2.5 ma per amplifier
OPA2134 checked out...not good... ~0.96ma, so ~0.5 ma per amplifier, far from the 4 to 5 range the datasheet says
This is closer to a LM358 or something, no idea
Anyways, I have a mouser cart filling up with some other stuff so I will probably replace it from there...
The photo shows a pretty poor looking BB logo (regular font?) and a missing pin 1 indent?
So I setup the quiescent current sanity check test with the OPA2134 and some TL072 I have on hand (also from Tayda)
The results weren't promising:
TL072 checked out pretty normal/to spec ~ 4.5ma, so ~2.25 per amplifier, datasheet says 1.4-2.5 ma per amplifier
OPA2134 checked out...not good... ~0.96ma, so ~0.5 ma per amplifier, far from the 4 to 5 range the datasheet says
This is closer to a LM358 or something, no idea
Anyways, I have a mouser cart filling up with some other stuff so I will probably replace it from there...
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New OPA2134 from mouser came today
Popped it in and the sound I was hearing is gone, General Tso is perfect now.
I performed the same test with the unity gain setup and got 8.48mA so basically exactly matching the datasheet (vs the 0.96mA I got for whatever the Tayda chip is/was)
Top is fake, bottom is new one. The logo is probably the biggest smoking gun (besides the fact that I heard the problem with my ears first which is excellent in this sort of situation)
Popped it in and the sound I was hearing is gone, General Tso is perfect now.
I performed the same test with the unity gain setup and got 8.48mA so basically exactly matching the datasheet (vs the 0.96mA I got for whatever the Tayda chip is/was)
Top is fake, bottom is new one. The logo is probably the biggest smoking gun (besides the fact that I heard the problem with my ears first which is excellent in this sort of situation)
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hamerfan
Well-known member
whats your IC Tester?
It looks identical this listing from Aliexpress:
It does seem to correctly identify many of the op amps used in guitar pedals. More just for peace of mind and curiousity than anything else
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