This circuit, published in the 1980s, can be applied to operational amplifiers of almost any type. The power supply must be symmetrical.
This second-order filter was found in a documentation from the 90's. It can be implemented with...
Charcoal microphones are rare today. In the figure we have a circuit that shows the use of one of...
This circuit was obtained from an English publication from 1977. The integrated circuit is a...