Gates#

Gates make decisions.

A logic gate turns one or more input levels into an output level according to a fixed rule. From this handful of rules — invert, require all, require any, and their negations and exclusives — every combinational function can be constructed. NAND and NOR are functionally complete: either one alone can build all the others, which is exactly why they became the workhorse products of the logic era.

Sections#

• NOT — Inversion: the simplest decision.
• AND — True only when all inputs are true.
• OR — True when any input is true.
• NAND — Universal gate; AND followed by inversion.
• NOR — Universal gate; OR followed by inversion.
• XOR — True when inputs differ.
• XNOR — True when inputs match.
• Schmitt Trigger — A gate input with hysteresis, for clean edges from slow or noisy signals.