74LS hex Schmitt inverter — what it is and where it fits
The SN74LS19AN is a hex inverter from the 74LS Schottky TTL family, with Schmitt-trigger inputs on all six gates. It takes a single input per inverter and outputs the logical complement, with built-in hysteresis that cleans up slow or noisy edges — useful for switch debouncing, oscillator circuits, or squaring up a waveform from a sensor. The 14-DIP through-hole package suits breadboard prototyping, legacy PCB retrofits, and designs that avoid surface-mount assembly. Supply range is 4.75 V to 5.25 V, commercial temperature grade 0°C to 70°C, so it is sized for benchtop, office, or indoor equipment — not the engine bay or a factory floor with wide thermal swings.
30 ns propagation delay — timing margin for a 5 V bus
Maximum propagation delay is 30 ns at 5 V supply and 15 pF load. Output drive is 400 µA source and 8 mA sink.
Active production — no LTB to plan around
TI lists the SN74LS19AN as Active, ROHS3 compliant. For a BOM line that needs a through-hole Schmitt inverter, this part is still a standard catalog item — not an allocation play, not a shortage-era panic buy. The 74LS family is mature but not sunset; you can qualify it into a new design without worrying about an EOL notice next quarter.