We found this circuit in an old English documentation. Transistors support modern equivalents. The circuit converts signals in the 5 to 15 MHz band for tuning into a common medium wave radio.
This circuit was obtained in a 1965 American magazine translation. The coil is formed by 40 + 40...
We found this circuit in a 1991 publication. What it does is to amplify a signal with unit gain...
This is the traditional configuration of a 6 or 12 V source with 7806 or 7812 integrated circuits, for a...