This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in the 1994 National Semiconductor Linear Applications Handbook.
This circuit is suggested by National Semiconductor and makes use of the negative regulator LM2990...
This circuit was found in a 90s Radio Electronics. MOSFETs must have excellent heat sinks and heat and...
An oscillator slightly different from the previous one also appeared in Radio Electronics magazine in...