This conventional filter circuit is from American documentation from the 1990s. The operational amplifier admits an equivalent and the power supply must be symmetrical.
This circuit was found in the January 1971 Radio Electronics magazine. It keeps the light flashing if...
This circuit is from the SGS manual of linear integrated circuits. The circuit can be implemented with...
Found in a 90s Hands On Electronics, this small preamp finds applications like microphones and other...