A notch for a narrow frequency band of a few per cent or even less normally requires close-tolerance components. At least, that’s what we thought until we came across a special opamp IC from Maxim. In ...

Electronic filters are signal processing circuits that attenuate unwanted frequency components from a signal. Before transistors and integrated circuits were discovered, coils of wire with large ...

The (Henry P.) Hall network is a widely tunable notch filter,tuned by a pot. It was a key part of the GR1232A (1961) It's still useful today. Here's how to design one. Fig 1. Shown is the original ...