This ultra-low noise amplifier and simple power supply was found in Analog Devices documentation from the 90's. The circuit can be implemented with modern equivalent components.
This operational amplifier circuit with variable gain was obtained in an 80's Electronic...
This audio mixer or mixer was found in a translation of an American publication from the 1980s. The...
September 2017 - Mouser Electronics already has the AP431S adjustable regulator from Diodes...