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Passive Filter Circuits

 

Last Updated: October 18, 2017 05:04 AM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

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. . . Circuit by David Johnson P.E.-June, 2000

Band pass Filter & Product Detector-  Scroll down to find this one.  Please refer to Figure 2.  The second stage constructed was the double tuned band pass filter.  You will need about 50-54 pF to resonate L1 and T1 at 7.040 MHz.  The C1 and C2 values chosen are thus perfect for tuning the 40 Meter CW band.  I peaked my particular front end filter at a center frequency of 7.025 MHz using a 50 ohm output impedance RF generator and then did some fine tuning with an antenna connected after the receiver was constructed. __

Bandpass Filter #1-  This circuit is taken from Progressive Communications Receiver in most of recent ARRL Handbooks.  Values for40 meter band are shown. __ Designed by Web David White, WN5Y

Bandpass filter features adjustable Q & constant maximum gain-  3-Mar-05 EDN Design Ideas:  Applications such as audio equalizers require bandpass filters with a constant maximum gain that's independent of the filter's quality factor, Q.  However, all of the well-known filter architectures—Sallen-Key, multiple-feedback, state-variable, and Tow-Thomas—suffer from altered maximum gain when Q varies __ Circuit Design by Herminio Martínez, Joan Domingo, Juan Gmiz, and Antoni Grau, Technical University of Catalonia, Barcelona, Spain

Band-reject filter includes compensation-  04/13/00 EDN Design Ideas:  Some band-reject LC filters employ a reactance to decouple individual resonators.  One such filter uses relatively small shunt inductors to decouple series resonators, known as a top-L coupling.  This type of coupling readily achieves narrow filter bandwidths while __ Circuit Design by Richard M Kurzrok, RMK Consultants, Queens Village, NY

Cheap Crystal filter-  Ladder filter using six 4.43MHz Crystals.  Building cheap side band filter for your home brew SSB Rig__

High IF Sampling Receiver Front End with Band-Pass Filter -  The modified AD9642-250EBZ board contains the circuit evaluated as described in this note, and the HSC-ADC-EVALCZ data capture board is used in conjunction with VisualAnalog® evaluation software, as well as the SPI Controller software to properly control the ADC and capture the data.  App Note AN-835 contains complete details on how to set up the hardware and software to run the tests described in this circuit note. __ Analog Devices from the Lab

LC filter Design on-line calculator-  This is an interactive design package for designing analogue (i.  e.  hardware) filters made of inductors and capacitors (Ls and Cs).  Fill in the form and press the ``Submit'' button, and a filter will be designed for you. __ Designed by Tony Fisher

Low pass filter for subwoofer-  The acoustic spectrum is extended by very low frequencies 20Iz and reaches as the 20000Iz in high frequencies.  In the low frequencies is degraded the sense of direction.  This reason us leads to the utilization speaker for the attribution of very low frequencies.  The manufacture that to you we propose distinguishes these frequencies, in order to him we lead to the corresponding amplifier.  The acoustic filters are met in various points in the sound systems. __

Low Pass Filter, 3Khz, with an 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 . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Notch Filter is DC Accurate-  03/02/95 EDN Design Ideas:  Most active filters exhibit noise, distortion, gain error, and dc offset.  However, a filter topology that separates the dc and ac paths can eliminate the last two of these unwanted behaviors (Fig 1a).  The dc path in this circuit has no op amps and, therefore, no dc offset.  The dc path does not have a dc gain error other than -6 dB of attenuation that the R1/R2 divider causes. (This attenuation is absent if you omit the R2 termination.) The ac path consists of C1 and a synthetic inductor comprising two wideband transconductance amplifiers and associated components.  The result is an active circuit that emulates the passive filter of Fig 1b __ Circuit Design by Gary Sellani, Maxim Integrated Products, Sunnyvale, CA

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 __ Designed by Bill Bowden

Variable Crystal Filter-  Crystal filters are often used for IF filters in receivers, where the bandwidth of this filter largely determines the selectivity of the receiver.  The unique feature of the filter described here is that the bandwidth has been made adjustable.  must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Variable Low Pass Filter-  A second order variable bandwidth low pass filter is formed using one IC and some passive components.  This low cost circuit is good out to 2.5MHz. __ Designed by Jim Haggerman, Hagerman Technology LLC

WIDE BANDWIDTH LOW COST SAW NOTCH FILTERS-  Surface Acoustic Wave (SAW) Notch Filters have been fabricated in the past with limited success.  A prevailing problem has been stopband null depth and bandwidth versus a reasonably broad passband response.  Typically, notch filters developed in the past have achieved either one or the other.  Notch Filters using the Single Phase Unidirectional Transducer (SPUDT) SAW notch element have achieved good null depth __ Designed by P.A. Lorenz and D.F. Thompson

Wideband filter uses image parameters-  26-Oct-00 EDN Design Ideas:  You can design various lowpass and highpass filters using image parameters (Reference 1 and Reference 2 ].  By cascading a highpass and a lowpass filter. PDF has several circuits, please scroll to find this one. __ Circuit Design by Richard M Kurzrok, RMK Consultants, Queens Village, NY


Passive Filter Circuits

 


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