This circuit uses NOR ports to generate signals up to 10 MHz, depending on the crystal. The supply can be done with voltages from 5 to 15 V and the signal generated is rectangular.
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...