This circuit was found in a 1967 General Electric documentation. Tunnel diodes can oscillate at very high frequencies. These are not currently easy to obtain components.
Found in a European magazine from the 1980s, this circuit can amplify signals from 10 kHz up to...
This circuit indicates whether a cable or wire is energized by simply approaching its antenna. The...
Suggested by Intersil in documentation from the 90's, this circuit is valid for modern operating...