Found in a 1970 documentation, this circuit makes use of 741 operational amplifiers that are common today. Note that the power supply must be symmetrical.
We found this circuit in a 1992 documentation. It can still be easily assembled today, as the...
This interesting configuration was found in an American factory documentation from the 1970s. The...
I found this circuit in a 1978 publication. The circuit can be assembled with a BD136 transistor to...