This circuit, which uses an unusual integrated, is from the Motorola Linear Databook of 1990. Transistors admit equivalents.
This TTL circuit for digital signals up to a few dozen megahertz was found in old documentation, but...
This circuit with an operational amplifier was found in the magazine Radio Electronics of...
This detector is from the 1990 Motorola Dataar Databook, but can be adapted to work with more...