Capacitance multiplier (CB7803E)

We found this circuit in an old Popular Electronics. The circuit can be applied to other operational amplifiers.

Amplifier with modulator (CB9176E)
This circuit with a double-gate MOS transistor was found in a Popular Electronics from the 90's....
Light relay (CB23551E)
This photoelectric cell light relay was found in Radio Electronics magazine from April 1958. The...
Cassette Tape Retriever (CB10832E)
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...