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 fires at the touch of a sensor, passing its output from high to low in a time given by...
This 9 V amplifier has a gain of 20 and provides a power of a few hundred milliwatts. The circuit is...
This circuit in its original version was found in an 1975 English publication. It is a...