We found this circuit in a Poptronics from the 90's. Equivalent operational amplifiers can be used. The circuit must be supplied by a symmetrical source.
In this circuit, Motorola's Linear Interface ICs, R3 is used to compensate to high source...
This powerful pushbutton uses a power MOSFET. We found it in a Popular Electronics magazine from...
This interesting circuit was presented in an article in Radio Electronics magazine in July 1979....