This circuit was found in a Popular Electronics from the 90's. It consists of the solid-state variation of the well-known grid-dip meter. MOSFET is a component not very easy to obtain these days.
The four gates of a 40111 IC are used in thes two-out circuit. The output chages their state in a...
This circuit is a digitally controlled variable capacitor. We found it in American documentation from...
This circuit was found in the January 1975 Radio Electronics magazine. The diodes are current...