Hex inverter with Schmitt-trigger inputs — the 5V noise-rejection workhorse
The SN74LS14NSR is a hex inverter from the 74LS bipolar TTL family, each of its six channels featuring a Schmitt-trigger input. The hysteresis cleans up slow edges, noisy clock lines, or switch-contact bounce before the logic stage sees it.
Output drive and timing — the bipolar TTL reality
The output drive is asymmetric: 400µA source, 8mA sink. The 22ns propagation delay at 5V with a 15pF load is fast enough for most 5V logic buses.
Schmitt-trigger thresholds — the noise budget
The input logic levels are 0.5V low and 1.9V high, with the Schmitt hysteresis between them. That 1.4V window rejects noise that would toggle a plain inverter.