I have a mission to build a dummy load to make a PSU test and found some schematics with a positive load. It worked like a charm.

[https://electronics.stackexchange.com/questions/447770/electronic-load-problem-turning-mosfet-on][1]

But there is no information about how to drain from PSU negative side 
I've searched all internet and no answers. 

Please, anyone could help?


  [1]: https://electronics.stackexchange.com/questions/447770/electronic-load-problem-turning-mosfet-on