Editing Logic gate (section)

==== Three-state logic gates ====
[[File:Tristate buffer.svg|thumb|320px|right|A three-state buffer can be thought of as a switch. If ''B'' is on, the switch is closed. If B is off, the switch is open.]]
{{Main|Three-state logic}}

A three-state logic gate is a type of logic gate that can have three different outputs: high (H), low (L) and high-impedance (Z). The high-impedance state plays no role in the logic, which is strictly binary. These devices are used on [[Bus (computing)|buses]] of the [[CPU]] to allow multiple chips to send data. A group of three-state outputs driving a line with a suitable control circuit is basically equivalent to a [[multiplexer]], which may be physically distributed over separate devices or plug-in cards.

In electronics, a high output would mean the output is sourcing current from the positive power terminal (positive voltage). A low output would mean the output is sinking current to the negative power terminal (zero voltage). High impedance would mean that the output is effectively disconnected from the circuit.