It serves as a reference, since today we can have simpler and more compact solutions. This circuit is from an Electronics Experimenter Handbook from 1992. The integrated circuits are from that time.
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...