This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in the 1994 National Semiconductor Linear Applications Handbook.
This configuration reaches a few tens of megahertz depending on the crystal and the FET....
January 2017 - The new Texas Instruments TLV354x series of operational amplifiers with 200 MHz...
This circuit was found in a National Semiconductor manual from the 1980s. The integrated circuits used...