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Active Filters: Low Pass
Active Filter -- Main Page
Last Updated on:
Monday, October 03, 2011 06:07 PM
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Circuits Designed by Dave
Johnson, P.E. : |
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3KHz LOW PASS FILTER PLUS AUDIO AMP
This circuit uses a switched capacitor filter IC from National Semiconductor to
filter signals with frequencies higher than the 3KHz
needed for voice audio. The schematic includes an audio amplifier
that is designed to drive a standard audio head phone. The circuit is
described in more detail in the receiver section of Dave
Johnson's Handbook
of Optical Through the Air Communications. (this
link is off-site)
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LOW PASS ACTIVE FILTER DESIGN COLLECTION
This is a collection of inverting and non-inverting active low pass filter
circuits. I included one, two, three, four and six pole filter circuits.
You can change the component value ratios shown, to achieve any frequency cut-off
you may need. The circuit does not specify an operational amplifier.
The circuits should be used to select the needed resistor and capacitor components
for a particular frequency knee and roll-off slope.
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Links to electronic circuits, electronic schematics, designs for
engineers, hobbyists, students & inventors:
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"Brick-wall" lowpass audio filter needs no tuning -
14-Sep-06 Issue of EDN Gyrator supercapacitors eliminate the
need for inductors in this 15-kHz filter.... [Design Idea by Diego
Puyal and Pilar Molina, University of Zaragoza, Zaragoza, Spain;
Edited by Brad Thompson and Fran Granville] |
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19 kHz MPX Low Pass Filter - This map, armored also
enables automatic MONO / MPX through a low-pass filter, even with a
multiplex on its entry by using an ON / ON, panning, the whole
spectrum MPX more RDS is sent to the synthesizer, on the other hand
when it is in a position MONO, the low-pass filter is activated and
share its cutoff frequency at 15 KHz, only modulation G + D is sent
to the synthesizer, as 19 KHz. 19 KHz carrier, the signal multiplex
and subcarrier 57 KHz is thereby eliminated, which provides ease of
use for example in a string of issue relay tuner, if the link
between the issuer Departure and receiver re-issue was not of good
quality stereo, you sufficient to switch to mono to improve sound
quality, you can then connect the RDS encoder at the re-issuer.
….(electronic schematic added 11/08) |
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1MV Offset Clock-Tunable Monolithic 5-Pole Lowpass Filter -
DN67 Design Notes (Linear Technology) (app note added 6/06)
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20 kHz MPX Low Pass Filter - This map, armored also enables automatic MONO /
MPX through a low-pass filter, even with a multiplex on its entry by using an ON / ON,
panning, the whole spectrum MPX more RDS is sent to the synthesizer, on the other hand
when it is in a position MONO, the low-pass filter is activated and share its cutoff
frequency at 15 KHz, only modulation G + D is sent to the synthesizer, as 19 KHz. 19 KHz
carrier, the signal multiplex and subcarrier 57 KHz is thereby eliminated, which
provides ease of use for example in a string of issue relay tuner, if the link between
the issuer Departure and receiver re-issue was not of good quality stereo, you
sufficient to switch to mono to improve sound quality, you can then connect the RDS
encoder at the re-issuer. ….(electronic schematic added 11/08) |
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3kHz Low Pass Filter Plus Audio AMP - This circuit uses a switched capacitor
filter IC from National Semiconductor to filter signals with frequencies higher than the
3KHz needed for voice audio. The schematic includes an audio amplifier that is designed
to drive a standard audio head phone. The circuit is described in more detail in the
receiver section of Dave Johnson's Handbook of Optical Through the Air Communications.
(this link is off-site) …. [Designed by David A. Johnson] |
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8-bit microcontroller implements digital lowpass filter - 24-Jan-08 Issue of
EDN A simple assembler routine fits a digital lowpass filter into a
microcontroller.... [Design Idea by Abel Raynus, Armatron International, Malden, MA] |
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Active 2nd Order Filters - The figures below illustrate using opamps as active
2nd order filters. Three 2nd order filters are shown, low pass, high pass, and bandpass.
Each of these filters will attenuate frequencies outside their passband at a rate of
12dB per octave or 1/4 the voltage amplitude for each octave of frequency increase or
decrease outside the passband....(electronic circuit added 7/03) |
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Active-Filter has Wideband Tuning Range - 03/28/96 EDN-Design Ideas: You can
use the basic building block of Figure 1and high-speed analog components to build a
second-order lowpass variable-frequency filter with excellent phase linearity (Figure
2]. Figure 1’s filter section includes a Miller integrator followed by a variable-gain
amplifier with overall feedback resistor R2. The overall dc gain is the ratio of R2 to
R1. This circuit has a transfer....[Design Idea added 4/02] [Rea Schmid, National
Semiconductor, Comlinear Products Group, Fort Collins, CO] [Design Idea by Rea Schmid,
National Semiconductor, Comlinear Products Group, Fort Collins, CO] |
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Adjustable Filter Provides Lowpass Response - 03/01/01 EDN-Design Ideas
You can configure simple lowpass filters as pi sections with nominal three-pole, 0.1-dB
Chebyshev response to provide a moderate amount of stopband selectivity. You can put
four of these filters into one enclosure and then select discrete-filtering steps by
using toggle switches. Manufacturers of commercially available stepped attenuators and
adjustable baseband.... [Design Idea by Richard Kurzrok, Queens Village, NY] |
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Applications for a DC Accurate Lowpass Switched-Capacitor Filter - AN20 Linear
Technology Discusses principles of operation of LTC1062 and helpful hints
for its application. Various application circuits are explained in detail with focus on
how to cascade two LTC1062s and how to obtain notches. Noise and distortion performance
are fully illustrated. |
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Audio AMP + 3kHz Filter - This circuit is the audio amp section for a complete
optical transmitter. The circuit amplifies and filters the voice audio signals from an
electret microphone. The circuit is described in more detail in the transmitter circuit
section of Dave Johnson's Handbook of Optical Through the Air Communications. (this link
is off-site) …. [Designed by David A. Johnson] |
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