This circuit was found in a British documentation from 1969. It can be implemented with modern transistors. The pass band is 6 MHz.
I found this circuit in an English magazine from July 1982. The circuit is still viable as all...
The circuit is from the 1990 Motorola Linear Databook. The circuit can be implemented with other...
This indicator makes use of an LM339 voltage comparator circuit that contains 4 internal...