How to test Op-amps? - Page 1
Forum section: electronics / beginners

author: Megawilsound
author_rank: Contributor
timestamp: July 28, 2020, 05:37:56 am
content: Hi allJust quick question but gessing a long answer lol.Just need to know how to test op-amps, can this be done with a multimeter or do I need to use an oscilloscope?ThanksMegawilsound.

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 28, 2020, 08:10:30 am
content: Opamp has many parameters so it is impossible to check it with multimeter. You have to have at least several especial test boards for testing each of parameter.If you are afraid of counterfeit one, the fake ones most often may have a lower frequency response. To check it you have to have a functional generator and oscilloscope. (And of cause you need to assemble test board).If you are talking about how to check a suspicious opamp if it is burned - there is a possibility to check it as simple and not accurate test with multimeter. You need the same but 100% good one, so you can compare the resistances between pins, between pins an power pins etc.

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2020, 09:43:26 am
content: It's fairly easy to test whether an op-amp works or not, but as mentioned above, much more difficult to verify it's genuine and not counterfeit.The easiest way to check an op-amp works, without an oscilloscope is to build a schmitt trigger oscillator circuit with it and use it to flash an LED.

author: David Hess
author_rank: Super Contributor
timestamp: July 28, 2020, 03:50:25 pm
content: The most effective simple tests involve sweeping the parameter to be measured with a function generator; this will reveal obscurities which indicate subtle damage and counterfeit parts. I would pay particular attention to input bias current over the common mode range. Check out National application note AN-24:https://www.ti.com/lit/an/snoa637/snoa637.pdf?ts=1595951371071

author: maxcy
author_rank: Newbie
timestamp: July 28, 2020, 08:48:10 pm
content: :popcorn:Been working as an electronic tech for decades. So the first thing is to check the VCC and grounds. If they are good check the DC voltage on the + and - pins, they better be the same or you can stop there, bad IC. Look at the input and output with a scope to see if that part is working and your not missing a connection to the next stage. Get a spray can of coolant and spray the IC to see is it internally shorted, you can see the coolant vaporize instantly if it is hot. You might even touch it with your finger looking for a hot one, but the coolant is better. I've never seen something wrong with the peripherals to the IC except once a leaky coupling cap. Gone are the days where shorted out tube components would burn out resistors and short caps. Don't forget to check the DC voltages at the inputs and output. The bias on the inputs is easy to figure out by looking at the schematic and resistors giving the bias to the input and knowing that the input has an infinite resistance. Just knowing the bias at one input will tell what the other one has to be because of how op amps work. If all of this gets nowhere just replace the IC, they are cheap enough. I've never found an op amp that was not working out of it's intended parameters.