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Operational amplifier tester

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2PAC Mafia

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Hi,

I have found this circuit on the net:

https://music-electronics-forum.com/t12777/

It´s a very simple tester but for me could be good just to test them in case of doubt. I already have an IC tester but for example LM358 is not in the test list of the device so I´ve been thinking in making a tester for this cases. In my place I always have to order to mainland components, waiting for them and paying shipment so sometimes is better to test components.

I already made testers for cristal oscillators, triacs and tiristors and some other useful simulators. In this case I´m looking for the best way to test operational amplifiers, if you have some better one or advice would be good.
 
I guess any test is better than none. But that tester as is could give misleading indications. If, for example, the output were stuck at or near the positive rail, or the inverting input were open-circuit, the LED would light. You could add a switch and pull-up resistor to pull the inverting input higher than the non-inverting input; which should turn the LED off.
Of course, even with that mod, the circuit can't test AC properties of the opamp.
 
Why do you need to test opamps? If you buy Name-Brand parts from a reputable distributor then they are not fakes and are extremely reliable.
Oh, are you stripping old used opamps from defective Chinese boards?

I designed an audio equalizer for a new speaker and had tens of thousands of circuits built locally, tested and sold. I also designed the tester for the equalizer that tested the equalization at 6 frequencies, gain, low distortion and low noise. It also tested current drain.
Only two failed the tests, one had its quad opamp IC mounted backwards and another had a shorted electrolytic capacitor. The ones that were sold never had one returned.
 
Ola, Como Estas. My wife is from Spain but I have never been there. It is closer to China than me so maybe a lot of fake Chinese opamps go there so he needs to test them.
 
Hi,

I guess any test is better than none. But that tester as is could give misleading indications. If, for example, the output were stuck at or near the positive rail, or the inverting input were open-circuit, the LED would light. You could add a switch and pull-up resistor to pull the inverting input higher than the non-inverting input; which should turn the LED off.
Of course, even with that mod, the circuit can't test AC properties of the opamp.

Yes, that is better.

Why do you need to test opamps? If you buy Name-Brand parts from a reputable distributor then they are not fakes and are extremely reliable.
Oh, are you stripping old used opamps from defective Chinese boards?

I designed an audio equalizer for a new speaker and had tens of thousands of circuits built locally, tested and sold. I also designed the tester for the equalizer that tested the equalization at 6 frequencies, gain, low distortion and low noise. It also tested current drain.
Only two failed the tests, one had its quad opamp IC mounted backwards and another had a shorted electrolytic capacitor. The ones that were sold never had one returned.

In this case the reason is because a repair of some boards, I see problems at PFC circuit in some professional Fitness treadmill controllers and each one has 5 LM358 and some more components. Due to this I was thinking about making a tester just to know more about the failure because I know I can receive more of these units to be repaired.
2PAC, I just Googled where you live because I wanted to know the part of the world your in. That place looks awesome, can I come visit :)

AG, he can't afford better parts due to his living on Beach front property :)



https://www.google.com/maps/place/P...0x12979259c61ac757:0xc40d5406c3d058c6!6m1!1e1

I already bought 40 LM358 just to replace them but I would like to know more about the problem for future repairs on these units. I buy from RS and Farnell usually.

Yes, my place looks very nice, a little island in Mediterranean sea.
 
If a low power LM358 is overloaded then of course it will fail.
Instead of testing opamps maybe you should test the voltages and currents in the circuit to see if the opamps are overloaded. All the detailed spec's are in the datasheet of the opamp.
 
If a low power LM358 is overloaded then of course it will fail.
Instead of testing opamps maybe you should test the voltages and currents in the circuit to see if the opamps are overloaded. All the detailed spec's are in the datasheet of the opamp.

This is how I found problems at the PFC circuit where I have a L4981AD controller. I supplied 15Vdc without Vac input (only voltage at PFC circuit) and I saw differences in consumption, a good one had 50mA and bad ones had 80mA, 200mA and 400mA. Touching components they were getting hot. IC´s involved are AD633, L4981, LM358 x 5 and HCF40106. Rest of components I can test with multimeter.

I attach some pictures. The board and the PFC circuit.
 

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I think this tester may be too simple for your needs. How about just making a test board that connects the op-amp as a amplifier (say a gain of 10) with some small load (say 1k), and allows a quick and easy way for you to hook up a power supply, signal generator and an oscilloscope? This way you can get a good overall idea of how the op-amp is performing.

I don't think you need to do any complex or accurate testing, but just have a test jig that's quick to use. After all, you already have a reasonable set of test gear (as far as I know).
 
If you just want to test for "Go/No Go" of the op-amp, then there is one op-amp tester published on the 03/2005 Elektor Magazine. It can test single, dual and quad op-amps of a few common varieties. Just have a look at the article attached.
 

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I think this tester may be too simple for your needs. How about just making a test board that connects the op-amp as a amplifier (say a gain of 10) with some small load (say 1k), and allows a quick and easy way for you to hook up a power supply, signal generator and an oscilloscope? This way you can get a good overall idea of how the op-amp is performing.

I don't think you need to do any complex or accurate testing, but just have a test jig that's quick to use. After all, you already have a reasonable set of test gear (as far as I know).

Yes, that is the idea, I want to complete my workshop instruments as I'm getting new problems or needs.

If you just want to test for "Go/No Go" of the op-amp, then there is one op-amp tester published on the 03/2005 Elektor Magazine. It can test single, dual and quad op-amps of a few common varieties. Just have a look at the article attached.

That one is a good option, thanks for sharing it.
 
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