This is a tileable green circuit build for the mid game. With red belts and assembly machine 3's, it can be tiled four times before it becomes starved for copper.
I don't remember who came up with this design originally, but please add a comment below if you know. I've been using it for a long time, since 0.13.
Yellow belt version: https://factorioprints.com/view/-Kl-NTpuTXPVfk0N0EMo