Found in documentation from the 1980s, this circuit uses an operational amplifier from that time. Transistors are also from the era, and general-purpose equivalents can now be used.
This circuit was published in a 1979 magazine, but it can still be easily assembled as the...
The integrated circuit of this amplifier is not very common today. The output transistors can be...
Found in an old documentation about neon lamps, this circuit has the frequency basically...