This circuit tunes MW radios to apply the signal to a good audio amplifier. The circuit is from an old documentation. Transistors are general purpose types.
This circuit is from a Radio Electronics magazine from August 1960. It is a commercial circuit for marine...
We found this filter in documentation from the 1980s. The operational amplifier used is uncommon...
In this circuit, a light-sensitive SCR or Light Activated SCR determines the operation of an...