This automotive grade circuit was found in a 1991 Electronics Hobbyist. The transistors are general purpose types. P1 sets the monitoring voltage.
This ultra-low distortion driver was found in 80's Analog Devices documentation. The circuit has a...
This second-order filter was found in a documentation from the 90's. It can be implemented with...
This circuit goes into operation producing a sound on a small speaker when the supply voltage...