29.85 MHZ Notch Filter Schematic:

Adjustable 60Hz Filter: to filter out any HUM that may be picked up by a noisy power supply or long wire connection

Adjustable Audio Notch Filter:

Audio Notch Filter:

Basic Introduction to Filters: application notes on active, passive and switched capacitor filters, document in PDF format

Build an adjustable high frequency notch filter: 02/06/03  EDN-Design Ideas / Although you can obtain universal, resistor-programmable switched-capacitor filters that are configurable as notch filters, most cannot operate at bandwidths higher than 100 kHz. Further, the typically 16

Closing the loop deepens notches: 02/07/2002  EDN - Design Ideas / Notch filters remove a single unwanted frequency from an input signal. They are also a vital component of pulse-shaping networks, such as time-averaging filters. You can tune a state-variable filter over a wide range by changing the time constants of its integrating amplifiers (references 1, 2, and 3). .

CW Filters:

Helical Resonator Notch Filter:

High Q Notch Filter: National Semiconductor Application Notes first published28-Jun-1996

Inversal Notch and Bandpass Filter:

Notch Filter is DC Accurate: 03/02/95 EDN Design Ideas

Notch Filter uses only Lowpass Filters: 04/10/97 EDN Design Ideas

RC Notch Filter Twin T: The twin T notch filter can be used block an unwanted frequency or if placed around an op-amp as a bandpass filter. The notch frequency occurs where the capacitive reactance equals the resistance Xc=R and if the values are close, the attenuation can be very high and the notch frequency virtually eliminated.

Single Supply Sallen Key Notch Filter: