# Opamp Testing Project

**URL:** <https://forum.quantasylum.com/t/opamp-testing-project/755>\
**Category:** QA40x\
**Created:** [November 15, 2022, 4:46pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755 "2022-11-15T16:46:35Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\
**Post date:** [November 15, 2022, 4:46pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755/1 "2022-11-15T16:46:35Z")

</div>

Please feel free to discuss the blog post linked below related to characterizing opamps.

> **[Characterizing Opamps](https://quantasylum.com/blogs/news/characterizing-opamps)**
>
> Modern opamp specs are amazing. They come to us in a compact PDF form with outstanding vector color graphics, making it easy to know an enormous amount about the part under consideration. This is in sharp contrast to specs from decades ago, where...

---

<div class="post-metadata">

**Author:** ![Joop99](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@Joop99](https://forum.quantasylum.com/u/Joop99)\
**Post date:** [November 17, 2022, 8:59pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755/2 "2022-11-17T20:59:21Z")

</div>

Interesting project Matt, will this be a next “QAxxx” system? Could be something for testing op amps when your busy with some audio projects.

---

<div class="post-metadata">

**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\
**Post date:** [November 22, 2022, 11:00pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755/3 "2022-11-22T23:00:54Z")

</div>

Maybe, once the other products get updated and/or the shortage has resolved. I think the board is a bit specialized for what most need these days, especially considering how good data sheets are. But what would be helpful (for me) is the ability to specify a list of tests, and then compare two opamps side by side on the exact same tester.

The output impedance contribution really matters at these distortion levels, and the ability to understand a lower bound for a load is important, because the tradeoff is noise. So, it’s a constant balance between distortion and noise.

---

<div class="post-metadata">

**Author:** ![DanClark](https://avatars.discourse-cdn.com/v4/letter/d/d26b3c/32.png) [@DanClark](https://forum.quantasylum.com/u/DanClark)\
**Post date:** [January 7, 2023, 10:57pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755/4 "2023-01-07T22:57:45Z")

</div>

Interesting project, thanks for sharing.

The citations were also illuminating… we may build this tester rig to use with both our QA and our new AP555 systems, it looks quite functional!

---

<div class="post-metadata">

**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\
**Post date:** [January 9, 2023, 4:47pm UTC](https://forum.quantasylum.com/t/opamp-testing-project/755/5 "2023-01-09T16:47:09Z")

</div>

Hi @DanClark, the reality agrees well with the theory from the paper. In the plot below, you can see the opamp configuration 5A has a bit of crossover present (LM358) in inverting gain (20 dB) config. It’s hard to see the distortion in the time domain, but the residual display shows it clearly. In configuration 5B, the distortion is magnified to the point it’s readily visible in the time domain.

 ![image](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/9/93d4fb1906a180799d6e1d570754026b955f4057.png)

 ![image](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/3/3ea6db46c2504277f83b0c86699af34e5ccc47b9.png)