Electronic Terms for Engineers

IC Magnitude Comparator Chips

The graphic shows one example of a Magnitude Comparator. The same function could also be represented using different logic gates.

8-input Magnitude Comparator IC, logic diagram view
8-input Magnitude Comparator Circuit

Magnitude Comparator. This Magnitude Comparator can be used perform comparisons of two 8-bit binary or BCD words. The output provides both a P equals Q function or P greater than Q function.

A Magnitude Comparator would be considered standard logic or glue logic when a discrete IC is used. However, because of the internal complexity, a Magnitude Comparator would also be considered an MSI Function [Medium Scale Integration].
A similar function is the Identity Comparator.

Magnitude Comparator by Function:
Note in most cases when a 54xx device is listed, a 74xx device is also available.
74xx represents the commercial temperature range and 54xx represents the military variant, or industrial temperature range [IC Prefixes]. In either case the component grade that seemed to still be in production is listed.

54LS85 4-Bit Magnitude Comparators

74ALS518 8-Bit Identity Comparators (P=Q) w/ Enable, Open Collector Outputs, 20K Ohm Q-Input Pullup Resistor

54ALS520 8-Bit Identity/Magnitude Comparators (P=Q) with Enable and 20K Ohm Q-Input Pullup Resistors

74F521 8-Bit Identity/Magnitude Comparators (P=Q) with Enable

54LS682 8-Bit Identity/Magnitude Comparators

54LS684 8-Bit Identity/Magnitude Comparators

54ALS688 8-Bit Identity/Magnitude Comparators (P=Q) with Enable

54AS885 8-Bit Magnitude Comparators

54HCT85 4-Bit Magnitude Comparator

54HC85 4-Bit Magnitude Comparator

54HC688 8-Bit Identity/Magnitude Comparators (P=Q) with Enable

4063 [CMOS] 4-Bit Magnitude Comparators

4585 [CMOS] 4-Bit Magnitude Comparators

Using a Magnitude Comparator in a circuit assumes the designer either has no available programmable IC or no available input pins on the programmable device. Because using such a large IC to perform this simple function is not the best usage of board space.

Editor note; the 4000 series of parts were the common line of completely CMOS parts, with all of their internal gates being CMOS. A second line or generation was developed using the 4500 series of part numbers. However I don't know that the pining remained the same between the two series of parts, or if they reused the same function numbers. That is; could a 4563 part be a direct replacement for a 4063, or even if a 4563 part was ever produced. However the point is a small one, because in general the CMOS families are out-dated, and are only found in a small niche.

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