CD4011 is a member of the CD40xx CMOS IC series. The CD4011 IC contains four independent NAND gates. The devices perform the Boolean function Y = A × B or Y = A + B in positive logic. This IC is used in AV Receivers, Portable Audio Docks, and Blu-Ray Players.
The CD74HCT20M is a high speed CMOS Logic dual 4-input NAND Gate. The logic gates utilize silicon gate CMOS technology to achieve operating speeds similar to LSTTL gates with the low power consumption of standard CMOS integrated circuits.
The CD4012 is a CMOS technology based, 4-input NAND gate Dual package, i.e. the IC has two NAND gates which can operate independently and each gate can take in four Inputs. It is commonly used in buffer circuits, logic inverter circuits etc.