This high quality circuit with complementary symmetry was found in an Electronics World of 1966. It can be made with modern transistors like the BD or TIP series.
This circuit can work with almost any JFET. The circuit is from an Electronics Now from April...
This physical line servo control uses components that are not currently common. The circuit is from...
This circuit was found in a British documentation from 1969. It can be implemented with modern...