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Active Filters: Low Pass
 Low Pass Filters:   #'s - A        B - F       G - P      S - Z
Active Filter -- Main Page
Last Updated on:
Tuesday, August 18, 2015 06:50 AM

Circuits Designed by Dave Johnson, P.E. :
  • 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 Dave Johnson P.E.,  06/04/00]

  • Active Low Pass Filter Designs  -  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 . . . [Circuit by David Johnson P.E.,  12/10/00]

  • 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 . . . [Circuit by David A. Johnson P.E.,  06/04/00]

  • Low Pass Active Filter Designs  -  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 . . . [Circuit by David A. Johnson P.E.,  12/10/00]


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

1 Resistor Tunes Lowpass Filter -  08/21/03  EDN Design Idea   Any tunable, second-order, active RC-filter section requires at least two thoroughly matched variable resistors. But the lowpass implementation in Figure 1 provides for wide-range cutoff-frequency control using only a single variab… [by Vladimir Tepin, State Radioengineering University, Taganrog, Russia]

 

1.8V, 140uA, 100kHz, Lowpass Filter (Single-Ended Input and Differential Output) -  The LTC6256 circuit shown here is a 2nd order, 100kHz, Butterworth lowpass filter. The filter’s differential output maximizes the dynamic range in very low voltage operation. The LTC6255/LTC6256/LTC6257 are single/dual/quad operational Amplifiers with low noise, low power, low supply voltage, rail-to-rail input/output… [Linear Technology App Note - , Jul 20th 2010

 

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.…

 

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.… [Designer's name not included]

 

20 kHz MPX Low Pass Filter -  Cette carte, blindée elle aussi, permet la commutation automatique MONO/MPX grâce à un filtre passe-bas, même avec une source multiplex sur son entrée, par l'utilisation d'un interrupteur ON/ON. En position stéréo, tout le spectre MPX plus RDS est envoyé au synthétiseur. Par contre, lorsque celui-ci est en position MONO, le filtre passe-bas est activé, et de par sa fréquence de coupure à 15 KHz, seule la modulation G + D est envoyée au synthé.… [Designer's name not included]

 

3Khz Filter + Audio Amplifier -  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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/04/00]

 

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 Dave Johnson P.E.,  06/04/00]

 

3rd Order Filter-Using Model 425  -  No description, just schematic - OpAmps Lab Inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power), Switchers (Routing / Assign / Matrix), Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems. … [Application OpAmps Lab Inc.]

 

440 Hertz Peaked Low Pass Audio Filter Experiments -  At audio frequencies, low pass filtering can go a long way to improving CW and beacon reception. It has a been a long time since I built one and therefore decided to experiment with some designs using the 5532 op Amp… [Todd, VE7BPO]

 

8-Bit Microcontroller Implements Digital Lowpass Filter -  01/24/08  EDN Design Idea   A simple assembler routine fits a digital lowpass filter into a microcontroller… [by Abel Raynus, Armatron International, Malden, MA]

 

A Differential Input-to-Single-Ended Output Amplifier -  This circuit shows a circuit for converting a differential input to a single-ended output. For a gain equal to one (R1 = R2 = 604W and VOUT = V2 – V1) the input referred differential voltage noise density is 9nV/rtHz and differential input signal-to-noise ratio is 80.9dB with 0.2VRMS input signal in a 4MHz noise bandwidth.… [Linear Technology App Note, Jul 2, 2012]

 

A-weighting filter from an old Ampex service manual -  This filter circuit must be wriven with low impedance output and the putput of this circuit must be connected to very high impedance input. Second issue for the circuit is that, properly loaded, the circuit describe has about a 12. 4 dB insertion loss normalized at 1 kHz (A weighting, in fact, requires a "gain" of about 1. 3 dB at 2. 7 kHz or so). This insertion loss must be accounted for when used as the original poster describes. . . . 

 

A Single-Ended Input to Differential Output Amplifier -  This circuit shows a circuit for generating a differential signal from a single-ended input. The differential output noise is a function of the noise of the Amplifiers, the noise of resistors R1 and R2 and the noise bandwidth. For example, if R1 and R2 are each 200W, the differential output voltage noise density is 9.5 nV/ÖHz… [Linear Technology App Note - , Jul 2, 2012]

 

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… [Bill Bowden, designer]

 

Active Filter Has Wideband Tuning Range -  03/28/96 EDN Design Idea   . 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 in… [by Rea Schmid, National Semiconductor, Comlinear Products Group, Fort Collins, CO]

 

Active Low Pass Filter Designs -  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 . . . [Circuit by David Johnson P.E.,  12/10/00]

 

Active-filter circuit and oscilloscope inspect a Class D Amplifiers output -  12/01/06  EDN Design Idea   Ease debugging of bridge-output pulse-width-modulated audio amplifiers with this circuit… [by John Guy, Maxim Integrated Products Inc, Sunnyvale, CA]

 

Adjustable filter provides lowpass response -  03/01/01 EDN Design Idea   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… [by Richard Kurzrok, Queens Village, NY]

 

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.…

 

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 . . . [Circuit by David A. Johnson P.E.,  06/04/00]


        Low Pass Filters:   #'s - A        B - F       G - P      S - Z


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