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.
Of course, other frequencies can be generated by changing the components. The circuit generates a...
This circuit was found in a 1974 publication. It provides a tone indication of the temperature sensed by...
This spy transmitter can be plugged directly into a power outlet. The power comes from a regulated...