Electronics > Beginners
TL081 weird glitch
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magic:
And what's cheaper than LM358? ;)

Probably not even recycled chips. The prices of those tend to start around 30 cents on AliExpress, the LM358 fakes go for 10 cents ;D
wraper:

--- Quote from: magic on November 14, 2019, 05:23:27 pm ---And what's cheaper than LM358? ;)

--- End quote ---
You can make 5 times cheaper than LM358 if you want. Look at fake NE5532 die shot, it's certainly not LM358. And it's simpler than LM358.
sheisthedarkness:

--- Quote from: imo on November 14, 2019, 05:21:50 pm ---Try to wire a few kohm resistor from opamp's output against Vcc. It could be the glitch disappears..

--- End quote ---
Just tried, no luck, same thing. How could this help exactly ?
magic:
It's RC4558 topology, another cheap classic opamp and more suited for audio. But I admit that in the case of fake 5532 I'm not entirely sure if it's an off the shelf die because it's just so tiny. I don't know if it meets the power dissipation specs of a real 4558 and for how long >:D Though on the second thought, some discrete transistors are even smaller, so who knows, perhaps it is a legit 4558 rather than a custom job.

But you are right, going for custom tiny underpowered and oversimplified designs will probably be the final step required to break the magic 10 cent barrier ;D


--- Quote from: sheisthedarkness on November 14, 2019, 05:34:16 pm ---Just tried, no luck, same thing. How could this help exactly ?

--- End quote ---
By biasing the output in class A. But the current conducted by the resistor at all time needs to be higher than the output current of the entire circuit. What kind of load is this opamp driving and what are the supply voltages?
sheisthedarkness:

--- Quote from: magic on November 14, 2019, 05:36:12 pm ---What kind of load is this opamp driving and what are the supply voltages?

--- End quote ---
Input is 1kHz about 2V pk-pk, supply voltages are + and -12V. I don't really need to get it working, I'm going to buy some real ones from digikey, I was just curious about your post.
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