This 50 Hz rejector or notch filter was found in a 1975 documentation. Other frequencies can be obtained by changing components. The filter uses a Wien network and must use a symmetrical power supply.
This circuit was found in 80's Popular Electronics. Transistors are commonly used. The...
This low current source uses some components that are hard to find in ours. The transformer is a...
This circuit is from a manual based on information from Japanese components from 1981. The power...