Quad 2-input AND gate in 14-SOIC — 74LS logic for 5 V boards
The Texas Instruments SN74LS08D is a quad 2-input AND gate from the 74LS Schottky-clamped TTL family, packaged in a 14-SOIC (3.90 mm width) for surface-mount assembly. It integrates four independent AND gates, each with two inputs, and operates from a 4.75 V to 5.25 V supply. The 74LS series balances speed and power — propagation delay is 20 ns at 5 V with a 15 pF load — making it a fit for legacy 5 V bus interfaces, control logic, and glue logic in commercial-temperature equipment (0°C to 70°C).
20 ns propagation delay — timing margin in a 5 V system
The 20 ns max propagation delay at 5 V and 15 pF load sets the timing budget for cascaded gates in address decoding, clock gating, or enable chains. In a 10 MHz bus with a 100 ns cycle, two LS08 gates in series eat 40 ns of margin — enough to matter if the path also includes a decoder or latch. The Schottky clamp reduces storage time versus standard TTL, so the delay is consistent across temperature and supply within the rated range.
Output drive and fan-out
Each gate sources 400 µA and sinks 8 mA at the output. That 8 mA sink can drive up to ten 74LS loads (each 0.4 mA input low current) directly, or a single standard TTL load. For driving a higher-current load like an LED or a relay coil, buffer the output with a transistor or a line driver — the 8 mA ceiling is firm.
Supply range and noise immunity
The 4.75 V to 5.25 V supply covers a nominal 5 V rail with ±5% regulation. Input low threshold is 0.8 V max, high threshold 2 V min, giving about 0.4 V of low-side noise margin and 0.7 V on the high side at 5 V. That is adequate for a clean backplane but marginal in a noisy industrial environment — the 74LS family was designed for controlled commercial settings, not factory-floor transients.
Temperature grade — commercial only
Rated 0°C to 70°C, this is a commercial-temperature device. It belongs in office equipment, appliances, test gear, and indoor telecom — not in an engine bay, outdoor enclosure, or cold warehouse. If the board sees -20°C or 85°C ambient, step to the 74LS08D's industrial sibling (SN74LS08D with a different suffix) or move to 74HC08D which offers wider temperature range.
Lifecycle and sourcing
The SN74LS08D carries an active lifecycle status and is ROHS3 compliant. For new designs, the 74LS family remains a valid choice for 5 V-only legacy systems where lower-power 74HC or 74HCT logic is not pin-compatible or where the Schottky speed is needed. Availability is confirmed through independent distribution; current pricing and lead time are quoted against an RFQ.