This small audio amplifier was found in an American publication in 1975, The integrated circuit used is rare today. The circuit was used in portable receivers of the time and other applications.
This second-order filter was found in American documentation and can be applied to almost any...
This circuit is based on documentation from the 1980s. It can be designed with modern operational...
This circuit is from an English magazine from 1978. The circuit can be assembled with BC557, BC547...