DM74LS85N

The DM74LS85N from National Semiconductor is a 4-bit magnitude comparator. This integrated circuit performs comparisons of straight binary and straight BCD (8-4-2-1) codes. It features three fully decoded decision outputs that are externally accessible. The device is designed for easy expansion to any number of bits without requiring external gates, allowing for the comparison of longer words by cascading multiple units.

Key electrical characteristics include a typical supply voltage of 5V, with a range from 4.75V to 5.25V, and a typical supply current of 10.4 mA. The operating temperature range is from 0°C to 70°C. The DM74LS85N is housed in a 16-pin DIP package and is suitable for through-hole mounting.

This comparator is expandable to any number of bits without external gates. Words of greater length can be compared by connecting comparators in cascade. The A > B, A < B, and A = B outputs of a stage handling less-significant bits are connected to the corresponding inputs of the next stage handling more-significant bits. The stage handling the least-significant bits requires a high-level voltage applied to the A = B input. The cascading paths are implemented with only a two-gate-level delay to reduce overall comparison times for long words.