I bought 20 LM741 off Ebay in summer of 2019 from the seller "satisfyelectronics" and it turns out that only 3 functioned as a LM741. After questioning my sanity for an entire afternoon, I eventually set up a dead simple unity gain circuit and tested every IC I had and only 3 functioned as expected.

All the non-functional ICs have relatively decent laser etching and it is indistinguishable from the chips that do work.

Fake LM741 that do not work
Fake LM741 that do not work

The entire order for the 20 LM741 was $1.88 USD with free shipping.

Addendum[edit | edit source]

After playing with a TL072CP op-amps which I thought had the same pinout as the LM741, I noticed that the TL072 exhibited the same behavior of these fakes and made me wonder if these fake chips are actually dual op-amps where Vcc is on pin 8 rather than pin 7. I re-tested the nonfunctioning LM741s with the pinouts of a TL072 dual op-amp in a unity gain configuration and both outputs had the expected output.

I think that someone took some other used dual op-amps and repackaged them as a LM741. Nevertheless, I have no doubt that all 20 of these are fake chips since they all have identical laser etching but totally different behavior.