This notch filter was found in National Semiconductor documentation from the 1980s. Operational amplifiers are from that era. The configuration can be adapted to use modern operational amplifiers.
This double tone generator uses a specific integrated circuit, having been found in a 1977 CMOS...
This circuit is used to test PNP or NPN transistors giving the status indication through LEDs. The...
This dimmer for incandescent lamps was obtained from an American 1990s documentation. The circuit...