This high impedance circuit was found in 1967 documentation by Ferranti. The original operational amplifier is from that time. The circuit can be implemented with modern equivalents.
This circuit is from 2001 documentation, serving to multiplex stereo signals for FM transmitters. The...
This circuit reverses the signal if both positive and negative. We found it in an American...
Found in a publication by Gernsback from 1960, this circuit makes use of germanium transistors of the time....