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Build an Adjustable High Frequency Notch Filter: 02/06/03 EDN Design Ideas / (added 12/04)
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. Furr, typically 16to 20-pin packages do not include a continuous-time, antialiasing
filter to prevent spurious signals from appearing at output....
Closing the Loop Deepens Notches: 05/07)/02 EDN Design Ideas / (added 12/04) 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). ...
High Q Notch Filter: National Semiconductor Application Notes first published28-Jun-1996 (app note added
4/02)
High-Q 60-Hertz Notch Filter: This high-Q notch filter is based on the "Twin-T" design. It produces
a very deep notch in the response curve at about 59.7 Hz. This is useful to remove 60-Hz hum and noise from audio recordings or live performances. Response is down over -60db at the center point. The LM3900 Norton opamp was chosen since it doesn't require extra components
for single-supply operation.... (circuit design added 7/06)
Notebook Power Supply has Two Outputs: 03/03/94 EDN-Design Ideas / (added 3/06) The
notebook-computer supply in Fig 1 powers the 5V logic and derives an adjustable -24V supply for an LCD's backplane. The design uses only a high-efficiency buck regulator (Si9150) and an NMOS/PMOS, dual-power-FET chip set (Si9943), eliminating the extra parts required when
you implement both supplies independently. Because of the low on-resistances of the dual FETs, this circuit can achieve better than 92% efficiency at 7.2V input and full-load output (7.6W)....
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. (added 4/02)
Reverse RIAA Equaliser: Test phono preamps for correct equalisation, or convert unused phono inputs.
(circuit added 6/07)
