Complex gate (AOI/OAI)
Beginner
A single gate that does a small combination of AND, OR and NOT in one step.
Novice
A CMOS gate whose pull-down network mixes series and parallel transistors, such as AND-OR-INVERT (AOI) or OR-AND-INVERT (OAI). It computes functions like NOT((A AND B) OR C) in one stage.
Expert
Also called compound gates. Any inverting function expressible as a series-parallel network can be one stage; AOI21, AOI22, OAI21 and OAI22 are library staples because they replace two or three simple gates with less area and delay. Stack depth limits how large they get.