Who here has the most unique job?

Electrical engineer with a specialization in analog design and test. (Graduate in december but I have a job lined up and an internship this summer so it counts) My last internship and the one I will be returning to this summer involved testing High Performance Analog devices. Along with test is characterization which, if you look at the pretty graphs in datasheets, is what char is about.

Test involves designing a test board that a handler (a giant loud ass machine that will place hundreds of devices a minute) will use to plug in every single IC before it gets shipped. The test board has to verify every parameter in the datasheet and once the solution is deployed, the board will run 24/7 verifying every IC before they are sold.

What is fun about it is how creative you can get. You have to understand the device inside and out, then use existing products to construct test circuits around this device. Normal use circuits, for say an op amp in your phone for playing music, require you to minimize noise and other non ideal parameters. In test you have to amplify the nonidealities to measure them. Some devices that my team deal with have fempto amp precision. How do you accurately measure a couple femptoamps when normal leakage is greater than that? And how do you do it repeatably and quickly? Those are part of the challenges of test engineering and solving those seemingly impossible issues are what makes it rewarding.

Here is another catch. What if your board is damaged? It might falsely fail every IC. My job last summer was to write diagnostics for a test board. When the machine started it, it first ran my code. It would report if a cap was out of spec, of an IC was damaged, if a certain op amp in the test loop was leaking too much. Etc. How do you test things that are meant to test other things? The challenge here was that I had to construct test circuits to test devices that were arranged in a test configuration for something completely different. Figuring that out was rewarding.

Also, how is this tied to design? If you know something about IC's the main purpose and benefit a couple decades ago was to construct op amps with the differential pairs back to back so that impurities present in one would be present in both and the circuit would still be matched. Now, what if the test engineer and designer work together, they can trim certain transistors on the wafer after it is manufactured and ensure that the device is matched where it needs to be.

So in addition to your diagnostics and test, you need to add some trim code to be able to fine tune the device. Isnt that cool?

One way of trimming is to use this huge million dollar laser that will actually cut transistors and reshape the internals of the wafer after it comes from the fab.

My next internship will focus on test board layouts that optimize certain tests. There are some very nuanced and finicky properties of PCB's, there are extra capacitances and inductances and leakages between every device, trace and layer. You can only simulate so much though. So we will build various ideas and characterize them and hopefully I can say, "layout x is best when you need to test characteristic y of device family z, and layout a is best for this characteristic b of device c" and when a new test board is designed for a new product, the test engineer can come to my research and be confident that the circuit will behave in a certain way because it has already been characterized in the way he needs.

/r/AskReddit Thread