Inside a Mystery 1980s Filter IC Featuring Switched Capacitors

What happened

Recently [Ken Shirriff] got handed a mystery IC by [CuriousMarc] who had found said IC in a box of various old chips. With the die under a microscope it was identified as a Harris HF10, itself a variant of the National Semiconductor MF10.

Labelled only with a date code of the 47th week of 1985 and a mysterious F1-10-5 alongside a logo that didn’t lead to any hits in the typical IC databases, it was up to [Ken] to figure out what lurks inside this CDIP chip. As it turns out, it’s actually a pretty interesting IC with an easy to identify die once the ceramic package had been cracked open with a surgical hammer-and-chisel strike.

This is a dual switched capacitor filter, with the modern version being e.g. Availability seems scarce, so the MF10 may not be long for this world.

Key facts

• Recently [Ken Shirriff] got handed a mystery IC by [CuriousMarc] who had — found: said IC in a box of various old chips