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Closing the Loop Deepens Notches - 05/07/02 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).....(design idea added 12/04)
Electric Field Disturbance Monitor-1 - This schematic is the power supply and
front-end sections of the field monitor that is discussed in more detail at Electric
Field Disturbance Monitor. The system can detect human and animal motion by the
electric fields they disturb. ….(designed by David A. Johnson)
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 .... (circuit design added 7/06)
Notch Filter is Insensitive to Component Tolerances - 03/02/00 EDN-Design Ideas:
Many approaches for creating notch filters, which reject a narrow band of frequencies
and pass all others, are unsatisfactory because they allow the component tolerances to
interact. The circuit in Figure 1a overcomes this limitation and enables easy
calculation of the component values for a desired notch frequency.....(design idea
added 2/06)
Notebook Power Supply has Two Outputs - 03/03/94 EDN-Design Ideas: 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)..../.....(design idea added
3/06)
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)
Switched capacitor IC forms notch filter - 09/30/99 EDN-Design Ideas: You can use
a switched-capacitor lowpass filter (LPF)to implement an inexpensive notch filter
(Figure 1a). The internal architecture of the IC (Figure 1b)includes summing nodes
similar to those nodes that analog-signal-processing stages use for feedback-error
generation. The IC lowpass-filters the quantity VIN2VCOM and adds VOS at the output.
In other words,.....(design idea added 10/06)
