I am interfacing 1.8V and 3.3V UART lines, and due to one of the module's UART lines being a boot-config pin, it cannot be pulled up during the boot process. The module manufacture recommends the transistor circuit below for the logic level shifting.
I actually tried routing these lines through a 1.8 to 3.3V logic level shifter IC I already had on my PCB. It is the second picture below, but with that set-up I had to cut the traces on the boot-config line just to get the module to boot properly.
But my question is with this transistor circuit, I wasn't given any other information but am assuming these are NPN transistors. Is this correct, and are there any other major considerations I should take into account when laying out the pcb?