This circuit was found in a Popular Electronics documentation from the 90s. It is possible to switch the frequency of an oscillator by voltage. The circuit can act as a shield.
This field effect transistor amplifier circuit in common gate or common port configuration is from an old...
This circuit was obtained in an old American documentation. The integrated circuit used is...
This zero crossing detector is of the 1993 Motorola Linear Interface ICs. The source is...