This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in the 1994 National Semiconductor Linear Applications Handbook.
This low Power output stage can source a fraction of watt to a small loudspeaker. The transformer...
This circuit is from a 1995 publication; The current is obtained by dividing 1.25 by R1. The...
This 1968 circuit uses Motorola power transistors of the time, providing 20 W of power with...