As Tri-state buffer has an added switch from the digital buffer, Tri-state Inverter has an additional switch than Digital Inverter as shown in Figure (a). This switch indicated by E, connects the input circuit to the output circuit whereby E is low. When E is high, the output circuit is disconnected from the circuit. Besides, when E is low it functions as a Digital Inverter. These states are listed in Truth Table of Figure (b). The symbol for Tri-state inverter is also illustrated in Figure (c).
(a) (b) (c)
Figure: (a) Switch Configuration, (b) Truth Table, and (b) Symbol of a Tri-state Inverter