This circuit was obtained in a 1970 engineering documentation. The operational is the 741, but other operational ones can be used. The power supply must be symmetrical.
Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be...
This amplifier stage, obtained in a 1980 publication, has a low input impedance and a high output...
This circuit was found in an American magazine in 1976. It doubles the frequency of TTL signals in the...