74S Schottky NOR gate — still on the active list
The Texas Instruments SN74S02N is a quad 2-input NOR gate from the 74S Schottky logic family, housed in a 14-pin DIP (0.300" body) for through-hole assembly. It runs on a 4.75V to 5.25V supply and is rated over the commercial 0°C to 70°C temperature range. The Schottky-clamped transistors give it a propagation delay of 5 ns at 5V into 50 pF — fast enough for 5V bus timing in older or cost-sensitive digital systems. Each of the four gates can sink 20 mA or source 1 mA at the output, so it drives standard TTL loads directly.
5 ns propagation delay — what it means for the bus
The 5 ns max delay at 5V and 50 pF is the figure that matters for timing closure. In a 5V system clocked at 20 MHz (50 ns period), a single gate eats 5 ns of the budget — fine for a few levels of logic, but you need to count the cumulative delay through a chain. The Schottky process keeps the edge rates clean, so signal-integrity reflections are less of a headache than with slower logic families. The input thresholds are standard TTL: 0.8 V low, 2 V high, so it will interface directly with 74LS, 74ALS, and other 5V TTL families without level translation.
Through-hole DIP — rework-friendly footprint
The 14-DIP package is about as rework-friendly as it gets. No thermal pad to worry about, no hidden balls — just clip the leads, pull the part, and solder in a replacement. The through-hole format also means the part survives a hot-air rework cycle without lifting pads, which matters for repair benches and legacy board rework.
Active lifecycle — no LTB pressure
The SN74S02N carries an Active product status, so there is no last-time-buy deadline or end-of-life notice to manage. It is ROHS3 compliant. For a 74S logic part that has been in production for decades, this means TI continues to manufacture it for the industrial and aftermarket base. You can qualify it into a new BOM without worrying about a sudden obsolescence-driven redesign.