Recently [Ken Shirriff] got handed a mystery IC by [CuriousMarc] who had found said IC in a box of various old chips. Labelled only with a date code of the …. Inside a Mystery 1980s Filter IC Featuring Switched Capacitors.
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. With the die under a microscope it was identified as a Harris HF10, itself a variant of the National Semiconductor MF10.
This is a dual switched capacitor filter, with the modern version being e.g. The TI MF10-N in both PDIP and SOIC, but sadly no CDIP any more. Availability seems scarce, so the MF10 may not be long for this world.
These filter ICs can tune their capacitors to act as a low-, band- or high-pass filter.
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