If you have the skills and can get your hands on SMD components, you can assemble this small amplifier. We found it in the Radio Electronics Experimenter special edition from 1990.
This circuit shows how to implement a negative resistance device with an operational amplifier. The...
This fast Schmitt trigger operates at frequencies from 10 Hz to 100 Hz, with very short rise time....
This circuit detects the presence of strong signals from spy transmitters, enabling their...