ACT as current sink and source at the output stage.Totem-pole TTL Configuration:The MAIN advantage of TTL with a "totem-pole" output stage is the low output resistance at output logical "1",also, the addition of an ACTIVE pull up the circuit in the output of the Gate results in the REDUCTION of propagation delay.Logic FamilyFull NameAdvantagesDisadvantagesCMOSComplementary metal-oxide-semiconductorLowest power consumptionUsed in all microcomputer chips today.Most COMMON logic family.Easily damaged by static discharge and voltage spikes.TTLTransistor-transistor logicEarliest developed.Most rugged.Least susceptible to electrical damage.Consumes more power than CMOS – not suitable for battery-operated devices.ECLEmitter-coupled logicFastest available logic familyConsumes more power than CMOS. It requires extreme care in the wiring.