Priority encoder for 8-line to 3-line conversion
The SN74LS148DR is a priority encoder from Texas Instruments' 74LS family, encoding eight active-low inputs into a three-bit binary output. The 1 x 8:3 circuit means a single encoder handles eight input lines, outputting the highest-priority active input's binary code.
Output drive and signal integrity
The rated output currents are 400 µA sourcing (high) and 8 mA sinking (low). That 20:1 asymmetry means the encoder drives CMOS logic inputs cleanly on the high side but has limited fan-out on the low side — a typical LS TTL load of 1.6 mA per input allows sinking five standard loads before the output voltage rises above V_OL(max).
Package and board integration
Supplied in a 16-SOIC package with a 3.90 mm body width and 1.27 mm pin pitch, the SN74LS148DR mounts on the board surface — the 0.154-inch width is the standard SOIC-16 footprint shared across the 74LS logic family, so a single PCB land pattern serves multiple encoder or decoder variants.