TC74VHC540FEL TC74VHC540F-EL TC74VHC540FK TC74VHC540FK(EL,K) TC74VHC540FS TC74VHC540FSEL TC74VHC540FT TC74VHC540FT(EL) TC74VHC540FT(EL,K) TC74VHC540FT(EL,M)