TC74VHC21 TC74VHC21F TC74VHC21F(EL,K,F) TC74VHC21F(ELKF) TC74VHC21F-EL TC74VHC21FK TC74VHC21FK(EL,K) TC74VHC21FK(ELPPK) TC74VHC21FN TC74VHC21FS